Recombination, Genetic: Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses.Homologous Recombination: An exchange of DNA between matching or similar sequences.Crossing Over, Genetic: The reciprocal exchange of segments at corresponding positions along pairs of homologous CHROMOSOMES by symmetrical breakage and crosswise rejoining forming cross-over sites (HOLLIDAY JUNCTIONS) that are resolved during CHROMOSOME SEGREGATION. Crossing-over typically occurs during MEIOSIS but it may also occur in the absence of meiosis, for example, with bacterial chromosomes, organelle chromosomes, or somatic cell nuclear chromosomes.Rad52 DNA Repair and Recombination Protein: A DNA-binding protein that mediates DNA REPAIR of double strand breaks, and HOMOLOGOUS RECOMBINATION.V(D)J Recombination: The process by which the V (variable), D (diversity), and J (joining) segments of IMMUNOGLOBULIN GENES or T-CELL RECEPTOR GENES are assembled during the development of LYMPHOID CELLS using NONHOMOLOGOUS DNA END-JOINING.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Meiosis: A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Integrases: Recombinases that insert exogenous DNA into the host genome. Examples include proteins encoded by the POL GENE of RETROVIRIDAE and also by temperate BACTERIOPHAGES, the best known being BACTERIOPHAGE LAMBDA.DNA Repair: The reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule which contained damaged regions. The major repair mechanisms are excision repair, in which defective regions in one strand are excised and resynthesized using the complementary base pairing information in the intact strand; photoreactivation repair, in which the lethal and mutagenic effects of ultraviolet light are eliminated; and post-replication repair, in which the primary lesions are not repaired, but the gaps in one daughter duplex are filled in by incorporation of portions of the other (undamaged) daughter duplex. Excision repair and post-replication repair are sometimes referred to as "dark repair" because they do not require light.Models, Genetic: Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Rad51 Recombinase: A Rec A recombinase found in eukaryotes. Rad51 is involved in DNA REPAIR of double-strand breaks.Gene Conversion: The asymmetrical segregation of genes during replication which leads to the production of non-reciprocal recombinant strands and the apparent conversion of one allele into another. Thus, e.g., the meiotic products of an Aa individual may be AAAa or aaaA instead of AAaa, i.e., the A allele has been converted into the a allele or vice versa.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Recombinases: A broad category of enzymes that are involved in the process of GENETIC RECOMBINATION.DNA Nucleotidyltransferases: Enzymes that catalyze the incorporation of deoxyribonucleotides into a chain of DNA. EC 2.7.7.-.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.VDJ Recombinases: Recombinases involved in the rearrangement of immunity-related GENES such as IMMUNOGLOBULIN GENES and T-CELL RECEPTOR GENES.Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.DNA Breaks, Double-Stranded: Interruptions in the sugar-phosphate backbone of DNA, across both strands adjacently.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Immunoglobulin Class Switching: Gene rearrangement of the B-lymphocyte which results in a substitution in the type of heavy-chain constant region that is expressed. This allows the effector response to change while the antigen binding specificity (variable region) remains the same. The majority of class switching occurs by a DNA recombination event but it also can take place at the level of RNA processing.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Saccharomyces cerevisiae: A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.Rec A Recombinases: A family of recombinases initially identified in BACTERIA. They catalyze the ATP-driven exchange of DNA strands in GENETIC RECOMBINATION. The product of the reaction consists of a duplex and a displaced single-stranded loop, which has the shape of the letter D and is therefore called a D-loop structure.Genetic Variation: Genotypic differences observed among individuals in a population.DNA, Fungal: Deoxyribonucleic acid that makes up the genetic material of fungi.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Attachment Sites, Microbiological: Specific loci on both the bacterial DNA (attB) and the phage DNA (attP) which delineate the sites where recombination takes place between them, as the phage DNA becomes integrated (inserted) into the BACTERIAL DNA during LYSOGENY.Chromosomes, Fungal: Structures within the nucleus of fungal cells consisting of or containing DNA, which carry genetic information essential to the cell.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.DNA Helicases: Proteins that catalyze the unwinding of duplex DNA during replication by binding cooperatively to single-stranded regions of DNA or to short regions of duplex DNA that are undergoing transient opening. In addition DNA helicases are DNA-dependent ATPases that harness the free energy of ATP hydrolysis to translocate DNA strands.Immunoglobulin Joining Region: A segment of the immunoglobulin heavy chains, encoded by the IMMUNOGLOBULIN HEAVY CHAIN GENES in the J segment where, during the maturation of B-LYMPHOCYTES; the gene segment for the variable region upstream is joined to a constant region gene segment downstream. The exact position of joining of the two gene segments is variable and contributes to ANTIBODY DIVERSITY. It is distinguished from the IMMUNOGLOBULIN J CHAINS; a separate polypeptide that serves as a linkage piece in polymeric IGA or IGM.Chromosome Pairing: The alignment of CHROMOSOMES at homologous sequences.DNA Damage: Injuries to DNA that introduce deviations from its normal, intact structure and which may, if left unrepaired, result in a MUTATION or a block of DNA REPLICATION. These deviations may be caused by physical or chemical agents and occur by natural or unnatural, introduced circumstances. They include the introduction of illegitimate bases during replication or by deamination or other modification of bases; the loss of a base from the DNA backbone leaving an abasic site; single-strand breaks; double strand breaks; and intrastrand (PYRIMIDINE DIMERS) or interstrand crosslinking. Damage can often be repaired (DNA REPAIR). If the damage is extensive, it can induce APOPTOSIS.Genetic Markers: A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.Crosses, Genetic: Deliberate breeding of two different individuals that results in offspring that carry part of the genetic material of each parent. The parent organisms must be genetically compatible and may be from different varieties or closely related species.Genes, RAG-1: Genes involved in activating the enzyme VDJ recombinase. RAG-1 is located on chromosome 11 in humans (chromosome 2 in mice) and is expressed exclusively in maturing lymphocytes.Exodeoxyribonucleases: A family of enzymes that catalyze the exonucleolytic cleavage of DNA. It includes members of the class EC 3.1.11 that produce 5'-phosphomonoesters as cleavage products.Genetic Linkage: The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.Gene Rearrangement: The ordered rearrangement of gene regions by DNA recombination such as that which occurs normally during development.Immunoglobulin Switch Region: A site located in the INTRONS at the 5' end of each constant region segment of a immunoglobulin heavy-chain gene where recombination (or rearrangement) occur during IMMUNOGLOBULIN CLASS SWITCHING. Ig switch regions are found on genes encoding all five classes (IMMUNOGLOBULIN ISOTYPES) of IMMUNOGLOBULIN HEAVY CHAINS.Chromosomes: In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Repetitive Sequences, Nucleic Acid: Sequences of DNA or RNA that occur in multiple copies. There are several types: INTERSPERSED REPETITIVE SEQUENCES are copies of transposable elements (DNA TRANSPOSABLE ELEMENTS or RETROELEMENTS) dispersed throughout the genome. TERMINAL REPEAT SEQUENCES flank both ends of another sequence, for example, the long terminal repeats (LTRs) on RETROVIRUSES. Variations may be direct repeats, those occurring in the same direction, or inverted repeats, those opposite to each other in direction. TANDEM REPEAT SEQUENCES are copies which lie adjacent to each other, direct or inverted (INVERTED REPEAT SEQUENCES).Gene Targeting: The integration of exogenous DNA into the genome of an organism at sites where its expression can be suitably controlled. This integration occurs as a result of homologous recombination.Bacteriophage lambda: A temperate inducible phage and type species of the genus lambda-like viruses, in the family SIPHOVIRIDAE. Its natural host is E. coli K12. Its VIRION contains linear double-stranded DNA with single-stranded 12-base 5' sticky ends. The DNA circularizes on infection.DNA Replication: The process by which a DNA molecule is duplicated.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Saccharomyces cerevisiae Proteins: Proteins obtained from the species SACCHAROMYCES CEREVISIAE. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Genome, Viral: The complete genetic complement contained in a DNA or RNA molecule in a virus.Exodeoxyribonuclease V: An ATP-dependent exodeoxyribonuclease that cleaves in either the 5'- to 3'- or the 3'- to 5'-direction to yield 5'-phosphooligonucleotides. It is primarily found in BACTERIA.Synaptonemal Complex: The three-part structure of ribbon-like proteinaceous material that serves to align and join the paired homologous CHROMOSOMES. It is formed during the ZYGOTENE STAGE of the first meiotic division. It is a prerequisite for CROSSING OVER.Restriction Mapping: Use of restriction endonucleases to analyze and generate a physical map of genomes, genes, or other segments of DNA.Recombinational DNA Repair: Repair of DNA DAMAGE by exchange of DNA between matching sequences, usually between the allelic DNA (ALLELES) of sister chromatids.DNA, Single-Stranded: A single chain of deoxyribonucleotides that occurs in some bacteria and viruses. It usually exists as a covalently closed circle.DNA, Cruciform: A cross-shaped DNA structure that can be observed under the electron microscope. It is formed by the incomplete exchange of strands between two double-stranded helices or by complementary INVERTED REPEAT SEQUENCES that refold into hairpin loops on opposite strands across from each other.Endodeoxyribonucleases: A group of enzymes catalyzing the endonucleolytic cleavage of DNA. They include members of EC 3.1.21.-, EC 3.1.22.-, EC 3.1.23.- (DNA RESTRICTION ENZYMES), EC 3.1.24.- (DNA RESTRICTION ENZYMES), and EC 3.1.25.-.Selection, Genetic: Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.DNA Transposable Elements: Discrete segments of DNA which can excise and reintegrate to another site in the genome. Most are inactive, i.e., have not been found to exist outside the integrated state. DNA transposable elements include bacterial IS (insertion sequence) elements, Tn elements, the maize controlling elements Ac and Ds, Drosophila P, gypsy, and pogo elements, the human Tigger elements and the Tc and mariner elements which are found throughout the animal kingdom.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Blotting, Southern: A method (first developed by E.M. Southern) for detection of DNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Gene Deletion: A genetic rearrangement through loss of segments of DNA or RNA, bringing sequences which are normally separated into close proximity. This deletion may be detected using cytogenetic techniques and can also be inferred from the phenotype, indicating a deletion at one specific locus.DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Chromosome Inversion: An aberration in which a chromosomal segment is deleted and reinserted in the same place but turned 180 degrees from its original orientation, so that the gene sequence for the segment is reversed with respect to that of the rest of the chromosome.Gene Rearrangement, B-Lymphocyte: Ordered rearrangement of B-lymphocyte variable gene regions coding for the IMMUNOGLOBULIN CHAINS, thereby contributing to antibody diversity. It occurs during the differentiation of the IMMATURE B-LYMPHOCYTES.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Genes, Fungal: The functional hereditary units of FUNGI.Nucleic Acid Heteroduplexes: Double-stranded nucleic acid molecules (DNA-DNA or DNA-RNA) which contain regions of nucleotide mismatches (non-complementary). In vivo, these heteroduplexes can result from mutation or genetic recombination; in vitro, they are formed by nucleic acid hybridization. Electron microscopic analysis of the resulting heteroduplexes facilitates the mapping of regions of base sequence homology of nucleic acids.Chromosomes, Bacterial: Structures within the nucleus of bacterial cells consisting of or containing DNA, which carry genetic information essential to the cell.Sister Chromatid Exchange: An exchange of segments between the sister chromatids of a chromosome, either between the sister chromatids of a meiotic tetrad or between the sister chromatids of a duplicated somatic chromosome. Its frequency is increased by ultraviolet and ionizing radiation and other mutagenic agents and is particularly high in BLOOM SYNDROME.Diploidy: The chromosomal constitution of cells, in which each type of CHROMOSOME is represented twice. Symbol: 2N or 2X.Endonucleases: Enzymes that catalyze the hydrolysis of the internal bonds and thereby the formation of polynucleotides or oligonucleotides from ribo- or deoxyribonucleotide chains. EC 3.1.-.Cell Line: Established cell cultures that have the potential to propagate indefinitely.RecQ Helicases: A family of structurally-related DNA helicases that play an essential role in the maintenance of genome integrity. RecQ helicases were originally discovered in E COLI and are highly conserved across both prokaryotic and eukaryotic organisms. Genetic mutations that result in loss of RecQ helicase activity gives rise to disorders that are associated with CANCER predisposition and premature aging.Haploidy: The chromosomal constitution of cells, in which each type of CHROMOSOME is represented once. Symbol: N.DNA Repair Enzymes: Enzymes that are involved in the reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule, which contained damaged regions.Genomic Instability: An increased tendency of the GENOME to acquire MUTATIONS when various processes involved in maintaining and replicating the genome are dysfunctional.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Genetic Vectors: DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.Transformation, Genetic: Change brought about to an organisms genetic composition by unidirectional transfer (TRANSFECTION; TRANSDUCTION, GENETIC; CONJUGATION, GENETIC, etc.) and incorporation of foreign DNA into prokaryotic or eukaryotic cells by recombination of part or all of that DNA into the cell's genome.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Sequence Alignment: The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.DNA, Recombinant: Biologically active DNA which has been formed by the in vitro joining of segments of DNA from different sources. It includes the recombination joint or edge of a heteroduplex region where two recombining DNA molecules are connected.Genes, Bacterial: The functional hereditary units of BACTERIA.Genes, Immunoglobulin: Genes encoding the different subunits of the IMMUNOGLOBULINS, for example the IMMUNOGLOBULIN LIGHT CHAIN GENES and the IMMUNOGLOBULIN HEAVY CHAIN GENES. The heavy and light immunoglobulin genes are present as gene segments in the germline cells. The completed genes are created when the segments are shuffled and assembled (B-LYMPHOCYTE GENE REARRANGEMENT) during B-LYMPHOCYTE maturation. The gene segments of the human light and heavy chain germline genes are symbolized V (variable), J (joining) and C (constant). The heavy chain germline genes have an additional segment D (diversity).Mutagenesis, Insertional: Mutagenesis where the mutation is caused by the introduction of foreign DNA sequences into a gene or extragenic sequence. This may occur spontaneously in vivo or be experimentally induced in vivo or in vitro. Proviral DNA insertions into or adjacent to a cellular proto-oncogene can interrupt GENETIC TRANSLATION of the coding sequences or interfere with recognition of regulatory elements and cause unregulated expression of the proto-oncogene resulting in tumor formation.Immunoglobulin Variable Region: That region of the immunoglobulin molecule that varies in its amino acid sequence and composition, and comprises the binding site for a specific antigen. It is located at the N-terminus of the Fab fragment of the immunoglobulin. It includes hypervariable regions (COMPLEMENTARITY DETERMINING REGIONS) and framework regions.Mutagenesis: Process of generating a genetic MUTATION. It may occur spontaneously or be induced by MUTAGENS.Haplotypes: The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.Fungal Proteins: Proteins found in any species of fungus.Chromosome Breakage: A type of chromosomal aberration involving DNA BREAKS. Chromosome breakage can result in CHROMOSOMAL TRANSLOCATION; CHROMOSOME INVERSION; or SEQUENCE DELETION.Bacterial Proteins: Proteins found in any species of bacterium.Linkage Disequilibrium: Nonrandom association of linked genes. This is the tendency of the alleles of two separate but already linked loci to be found together more frequently than would be expected by chance alone.Genetics, Population: The discipline studying genetic composition of populations and effects of factors such as GENETIC SELECTION, population size, MUTATION, migration, and GENETIC DRIFT on the frequencies of various GENOTYPES and PHENOTYPES using a variety of GENETIC TECHNIQUES.Deoxyribonucleases, Type II Site-Specific: Enzyme systems containing a single subunit and requiring only magnesium for endonucleolytic activity. The corresponding modification methylases are separate enzymes. The systems recognize specific short DNA sequences and cleave either within, or at a short specific distance from, the recognition sequence to give specific double-stranded fragments with terminal 5'-phosphates. Enzymes from different microorganisms with the same specificity are called isoschizomers. EC 3.1.21.4.Ultraviolet Rays: That portion of the electromagnetic spectrum immediately below the visible range and extending into the x-ray frequencies. The longer wavelengths (near-UV or biotic or vital rays) are necessary for the endogenous synthesis of vitamin D and are also called antirachitic rays; the shorter, ionizing wavelengths (far-UV or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants.Transposases: Enzymes that recombine DNA segments by a process which involves the formation of a synapse between two DNA helices, the cleavage of single strands from each DNA helix and the ligation of a DNA strand from one DNA helix to the other. The resulting DNA structure is called a Holliday junction which can be resolved by DNA REPLICATION or by HOLLIDAY JUNCTION RESOLVASES.B-Lymphocytes: Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Sequence Deletion: Deletion of sequences of nucleic acids from the genetic material of an individual.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.Methyl Methanesulfonate: An alkylating agent in cancer therapy that may also act as a mutagen by interfering with and causing damage to DNA.Escherichia coli Proteins: Proteins obtained from ESCHERICHIA COLI.Immunoglobulin Heavy Chains: The largest of polypeptide chains comprising immunoglobulins. They contain 450 to 600 amino acid residues per chain, and have molecular weights of 51-72 kDa.Schizosaccharomyces: A genus of ascomycetous fungi of the family Schizosaccharomycetaceae, order Schizosaccharomycetales.Bacteriophage P1: A species of temperate bacteriophage in the genus P1-like viruses, family MYOVIRIDAE, which infects E. coli. It is the largest of the COLIPHAGES and consists of double-stranded DNA, terminally redundant, and circularly permuted.Telomere: A terminal section of a chromosome which has a specialized structure and which is involved in chromosomal replication and stability. Its length is believed to be a few hundred base pairs.Viral Proteins: Proteins found in any species of virus.VDJ Exons: Exons that are created in vivo during LYMPHOCYTE maturation from the V, D, and J gene segments of immunoglobulin superfamily genes (e.g., the IMMUNOGLOBULIN HEAVY CHAIN GENES, or the T-CELL RECEPTOR BETA GENES or T-CELL RECEPTOR GAMMA GENES ) by the VDJ RECOMBINASE system.Nondisjunction, Genetic: The failure of homologous CHROMOSOMES or CHROMATIDS to segregate during MITOSIS or MEIOSIS with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none.Genetic Engineering: Directed modification of the gene complement of a living organism by such techniques as altering the DNA, substituting genetic material by means of a virus, transplanting whole nuclei, transplanting cell hybrids, etc.Polymorphism, Genetic: The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.Genetic Complementation Test: A test used to determine whether or not complementation (compensation in the form of dominance) will occur in a cell with a given mutant phenotype when another mutant genome, encoding the same mutant phenotype, is introduced into that cell.Cytidine Deaminase: An enzyme that catalyzes the deamination of cytidine, forming uridine. EC 3.5.4.5.Genome: The genetic complement of an organism, including all of its GENES, as represented in its DNA, or in some cases, its RNA.Sequence Homology: The degree of similarity between sequences. Studies of AMINO ACID SEQUENCE HOMOLOGY and NUCLEIC ACID SEQUENCE HOMOLOGY provide useful information about the genetic relatedness of genes, gene products, and species.DNA Topoisomerases: Enzymes that regulate the topology of DNA by actions such as breaking, relaxing, passing, and rejoining strands of DNA in cells. These enzymes are important components of the DNA replication system. They are classified by their substrate specificities. DNA TOPOISOMERASE I enzymes act on a single strand of DNA. DNA TOPOISOMERASE II enzymes act on double strands of DNA.Genes: A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms.DNA Restriction Enzymes: Enzymes that are part of the restriction-modification systems. They catalyze the endonucleolytic cleavage of DNA sequences which lack the species-specific methylation pattern in the host cell's DNA. Cleavage yields random or specific double-stranded fragments with terminal 5'-phosphates. The function of restriction enzymes is to destroy any foreign DNA that invades the host cell. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. They are also used as tools for the systematic dissection and mapping of chromosomes, in the determination of base sequences of DNAs, and have made it possible to splice and recombine genes from one organism into the genome of another. EC 3.21.1.Heterozygote: An individual having different alleles at one or more loci regarding a specific character.Holliday Junction Resolvases: Enzymes that recognize CRUCIFORM DNA structures and introduce paired incisions that help to resolve the structure into two DNA helices.Chromosomes, Plant: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of PLANTS.Cell Cycle Proteins: Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.Multigene Family: A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Epistasis, Genetic: A form of gene interaction whereby the expression of one gene interferes with or masks the expression of a different gene or genes. Genes whose expression interferes with or masks the effects of other genes are said to be epistatic to the effected genes. Genes whose expression is affected (blocked or masked) are hypostatic to the interfering genes.Immunoglobulin mu-Chains: The class of heavy chains found in IMMUNOGLOBULIN M. They have a molecular weight of approximately 72 kDa and they contain about 57 amino acid residues arranged in five domains and have more oligosaccharide branches and a higher carbohydrate content than the heavy chains of IMMUNOGLOBULIN G.Spores, Fungal: Reproductive bodies produced by fungi.DNA Breaks: Interruptions in the sugar-phosphate backbone of DNA.X Chromosome: The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species.Chromosome Deletion: Actual loss of portion of a chromosome.Pedigree: The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition.DNA End-Joining Repair: The repair of DOUBLE-STRAND DNA BREAKS by rejoining the broken ends of DNA to each other directly.Transformation, Bacterial: The heritable modification of the properties of a competent bacterium by naked DNA from another source. The uptake of naked DNA is a naturally occuring phenomenon in some bacteria. It is often used as a GENE TRANSFER TECHNIQUE.Genetic Techniques: Chromosomal, biochemical, intracellular, and other methods used in the study of genetics.Antigens, Nuclear: Immunologically detectable substances found in the CELL NUCLEUS.Adenosine Triphosphatases: A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.Pachytene Stage: The stage in the first meiotic prophase, following ZYGOTENE STAGE, when CROSSING OVER between homologous CHROMOSOMES begins.Replication Protein A: A single-stranded DNA-binding protein that is found in EUKARYOTIC CELLS. It is required for DNA REPLICATION; DNA REPAIR; and GENETIC RECOMBINATION.Genes, Viral: The functional hereditary units of VIRUSES.Gene Rearrangement, T-Lymphocyte: Ordered rearrangement of T-cell variable gene regions coding for the antigen receptors.Schizosaccharomyces pombe Proteins: Proteins obtained from the species Schizosaccharomyces pombe. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.DNA, Circular: Any of the covalently closed DNA molecules found in bacteria, many viruses, mitochondria, plastids, and plasmids. Small, polydisperse circular DNA's have also been observed in a number of eukaryotic organisms and are suggested to have homology with chromosomal DNA and the capacity to be inserted into, and excised from, chromosomal DNA. It is a fragment of DNA formed by a process of looping out and deletion, containing a constant region of the mu heavy chain and the 3'-part of the mu switch region. Circular DNA is a normal product of rearrangement among gene segments encoding the variable regions of immunoglobulin light and heavy chains, as well as the T-cell receptor. (Riger et al., Glossary of Genetics, 5th ed & Segen, Dictionary of Modern Medicine, 1992)RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Conjugation, Genetic: A parasexual process in BACTERIA; ALGAE; FUNGI; and ciliate EUKARYOTA for achieving exchange of chromosome material during fusion of two cells. In bacteria, this is a uni-directional transfer of genetic material; in protozoa it is a bi-directional exchange. In algae and fungi, it is a form of sexual reproduction, with the union of male and female gametes.Antibody Diversity: The phenomenon of immense variability characteristic of ANTIBODIES. It enables the IMMUNE SYSTEM to react specifically against the essentially unlimited kinds of ANTIGENS it encounters. Antibody diversity is accounted for by three main theories: (1) the Germ Line Theory, which holds that each antibody-producing cell has genes coding for all possible antibody specificities, but expresses only the one stimulated by antigen; (2) the Somatic Mutation Theory, which holds that antibody-producing cells contain only a few genes, which produce antibody diversity by mutation; and (3) the Gene Rearrangement Theory, which holds that antibody diversity is generated by the rearrangement of IMMUNOGLOBULIN VARIABLE REGION gene segments during the differentiation of the ANTIBODY-PRODUCING CELLS.Genes, Switch: Genes that cause the epigenotype (i.e., the interrelated developmental pathways through which the adult organism is realized) to switch to an alternate cell lineage-related pathway. Switch complexes control the expression of normal functional development as well as oncogenic transformation.Gene Rearrangement, B-Lymphocyte, Heavy Chain: Ordered rearrangement of B-lymphocyte variable gene regions of the IMMUNOGLOBULIN HEAVY CHAINS, thereby contributing to antibody diversity. It occurs during the first stage of differentiation of the IMMATURE B-LYMPHOCYTES.Chromosome Segregation: The orderly segregation of CHROMOSOMES during MEIOSIS or MITOSIS.Bacteriophages: Viruses whose hosts are bacterial cells.Chromatids: Either of the two longitudinally adjacent threads formed when a eukaryotic chromosome replicates prior to mitosis. The chromatids are held together at the centromere. Sister chromatids are derived from the same chromosome. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Immunoglobulin Constant Regions: The domains of the immunoglobulin molecules that are invariable in their amino acid sequence within any class or subclass of immunoglobulin. They confer biological as well as structural functions to immunoglobulins. One each on both the light chains and the heavy chains comprises the C-terminus half of the IMMUNOGLOBULIN FAB FRAGMENT and two or three of them make up the rest of the heavy chains (all of the IMMUNOGLOBULIN FC FRAGMENT)Genes, Mating Type, Fungal: Fungal genes that mostly encode TRANSCRIPTION FACTORS. In some FUNGI they also encode PHEROMONES and PHEROMONE RECEPTORS. The transcription factors control expression of specific proteins that give a cell its mating identity. Opposite mating type identities are required for mating.Base Composition: The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Genome, Fungal: The complete gene complement contained in a set of chromosomes in a fungus.Homozygote: An individual in which both alleles at a given locus are identical.Genome, Bacterial: The genetic complement of a BACTERIA as represented in its DNA.DNA Topoisomerases, Type I: DNA TOPOISOMERASES that catalyze ATP-independent breakage of one of the two strands of DNA, passage of the unbroken strand through the break, and rejoining of the broken strand. DNA Topoisomerases, Type I enzymes reduce the topological stress in the DNA structure by relaxing the superhelical turns and knotted rings in the DNA helix.Homeodomain Proteins: Proteins encoded by homeobox genes (GENES, HOMEOBOX) that exhibit structural similarity to certain prokaryotic and eukaryotic DNA-binding proteins. Homeodomain proteins are involved in the control of gene expression during morphogenesis and development (GENE EXPRESSION REGULATION, DEVELOPMENTAL).Somatic Hypermutation, Immunoglobulin: A programmed mutation process whereby changes are introduced to the nucleotide sequence of immunoglobulin gene DNA during development.Translocation, Genetic: A type of chromosome aberration characterized by CHROMOSOME BREAKAGE and transfer of the broken-off portion to another location, often to a different chromosome.Chromosomes, Mammalian: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of MAMMALS.Centromere: The clear constricted portion of the chromosome at which the chromatids are joined and by which the chromosome is attached to the spindle during cell division.Drosophila melanogaster: A species of fruit fly much used in genetics because of the large size of its chromosomes.Immunoglobulin gamma-Chains: Heavy chains of IMMUNOGLOBULIN G having a molecular weight of approximately 51 kDa. They contain about 450 amino acid residues arranged in four domains and an oligosaccharide component covalently bound to the Fc fragment constant region. The gamma heavy chain subclasses (for example, gamma 1, gamma 2a, and gamma 2b) of the IMMUNOGLOBULIN G isotype subclasses (IgG1, IgG2A, and IgG2B) resemble each other more closely than the heavy chains of the other IMMUNOGLOBULIN ISOTYPES.Polymorphism, Restriction Fragment Length: Variation occurring within a species in the presence or length of DNA fragment generated by a specific endonuclease at a specific site in the genome. Such variations are generated by mutations that create or abolish recognition sites for these enzymes or change the length of the fragment.Spermatocytes: Male germ cells derived from SPERMATOGONIA. The euploid primary spermatocytes undergo MEIOSIS and give rise to the haploid secondary spermatocytes which in turn give rise to SPERMATIDS.Meiotic Prophase I: The prophase of the first division of MEIOSIS (in which homologous CHROMOSOME SEGREGATION occurs). It is divided into five stages: leptonema, zygonema, PACHYNEMA, diplonema, and diakinesis.Chromosomes, Artificial, Bacterial: DNA constructs that are composed of, at least, a REPLICATION ORIGIN, for successful replication, propagation to and maintenance as an extra chromosome in bacteria. In addition, they can carry large amounts (about 200 kilobases) of other sequence for a variety of bioengineering purposes.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Gamma Rays: Penetrating, high-energy electromagnetic radiation emitted from atomic nuclei during NUCLEAR DECAY. The range of wavelengths of emitted radiation is between 0.1 - 100 pm which overlaps the shorter, more energetic hard X-RAYS wavelengths. The distinction between gamma rays and X-rays is based on their radiation source.Microsatellite Repeats: A variety of simple repeat sequences that are distributed throughout the GENOME. They are characterized by a short repeat unit of 2-8 basepairs that is repeated up to 100 times. They are also known as short tandem repeats (STRs).Prophase: The first phase of cell nucleus division, in which the CHROMOSOMES become visible, the CELL NUCLEUS starts to lose its identity, the SPINDLE APPARATUS appears, and the CENTRIOLES migrate toward opposite poles.DNA-Activated Protein Kinase: A serine-threonine protein kinase that, when activated by DNA, phosphorylates several DNA-binding protein substrates including the TUMOR SUPPRESSOR PROTEIN P53 and a variety of TRANSCRIPTION FACTORS.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Gene Rearrangement, B-Lymphocyte, Light Chain: Ordered rearrangement of B-lymphocyte variable gene regions coding for the kappa or lambda IMMUNOGLOBULIN LIGHT CHAINS, thereby contributing to antibody diversity. It occurs during the second stage of differentiation of the IMMATURE B-LYMPHOCYTES.Physical Chromosome Mapping: Mapping of the linear order of genes on a chromosome with units indicating their distances by using methods other than genetic recombination. These methods include nucleotide sequencing, overlapping deletions in polytene chromosomes, and electron micrography of heteroduplex DNA. (From King & Stansfield, A Dictionary of Genetics, 5th ed)Immunoglobulin kappa-Chains: One of the types of light chains of the immunoglobulins with a molecular weight of approximately 22 kDa.Sex Chromosomes: The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X CHROMOSOME, the Y CHROMOSOME, and the W, Z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth Bombyx mori, for example)). In such cases the W chromosome is the female-determining and the male is ZZ. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Lysogeny: The phenomenon by which a temperate phage incorporates itself into the DNA of a bacterial host, establishing a kind of symbiotic relation between PROPHAGE and bacterium which results in the perpetuation of the prophage in all the descendants of the bacterium. Upon induction (VIRUS ACTIVATION) by various agents, such as ultraviolet radiation, the phage is released, which then becomes virulent and lyses the bacterium.Coliphages: Viruses whose host is Escherichia coli.Genome, Human: The complete genetic complement contained in the DNA of a set of CHROMOSOMES in a HUMAN. The length of the human genome is about 3 billion base pairs.Immunoglobulin J-Chains: A 15 kD "joining" peptide that forms one of the linkages between monomers of IMMUNOGLOBULIN A or IMMUNOGLOBULIN M in the formation of polymeric immunoglobulins. There is one J chain per one IgA dimer or one IgM pentamer. It is also involved in binding the polymeric immunoglobulins to POLYMERIC IMMUNOGLOBULIN RECEPTOR which is necessary for their transcytosis to the lumen. It is distinguished from the IMMUNOGLOBULIN JOINING REGION which is part of the IMMUNOGLOBULIN VARIABLE REGION of the immunoglobulin light and heavy chains.DNA, Plant: Deoxyribonucleic acid that makes up the genetic material of plants.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Transgenes: Genes that are introduced into an organism using GENE TRANSFER TECHNIQUES.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Lod Score: The total relative probability, expressed on a logarithmic scale, that a linkage relationship exists among selected loci. Lod is an acronym for "logarithmic odds."Genome, Plant: The genetic complement of a plant (PLANTS) as represented in its DNA.Chromosomes, Human: Very long DNA molecules and associated proteins, HISTONES, and non-histone chromosomal proteins (CHROMOSOMAL PROTEINS, NON-HISTONE). Normally 46 chromosomes, including two sex chromosomes are found in the nucleus of human cells. They carry the hereditary information of the individual.

Different regulation of the p53 core domain activities 3'-to-5' exonuclease and sequence-specific DNA binding. (1/18933)

In this study we further characterized the 3'-5' exonuclease activity intrinsic to wild-type p53. We showed that this activity, like sequence-specific DNA binding, is mediated by the p53 core domain. Truncation of the C-terminal 30 amino acids of the p53 molecule enhanced the p53 exonuclease activity by at least 10-fold, indicating that this activity, like sequence-specific DNA binding, is negatively regulated by the C-terminal basic regulatory domain of p53. However, treatments which activated sequence-specific DNA binding of p53, like binding of the monoclonal antibody PAb421, which recognizes a C-terminal epitope on p53, or a higher phosphorylation status, strongly inhibited the p53 exonuclease activity. This suggests that at least on full-length p53, sequence-specific DNA binding and exonuclease activities are subject to different and seemingly opposing regulatory mechanisms. Following up the recent discovery in our laboratory that p53 recognizes and binds with high affinity to three-stranded DNA substrates mimicking early recombination intermediates (C. Dudenhoeffer, G. Rohaly, K. Will, W. Deppert, and L. Wiesmueller, Mol. Cell. Biol. 18:5332-5342), we asked whether such substrates might be degraded by the p53 exonuclease. Addition of Mg2+ ions to the binding assay indeed started the p53 exonuclease and promoted rapid degradation of the bound, but not of the unbound, substrate, indicating that specifically recognized targets can be subjected to exonucleolytic degradation by p53 under defined conditions.  (+info)

Evolutionary relationships of pathogenic clones of Vibrio cholerae by sequence analysis of four housekeeping genes. (2/18933)

Studies of the Vibrio cholerae population, using molecular typing techniques, have shown the existence of several pathogenic clones, mainly sixth-pandemic, seventh-pandemic, and U.S. Gulf Coast clones. However, the relationship of the pathogenic clones to environmental V. cholerae isolates remains unclear. A previous study to determine the phylogeny of V. cholerae by sequencing the asd (aspartate semialdehyde dehydrogenase) gene of V. cholerae showed that the sixth-pandemic, seventh-pandemic, and U.S. Gulf Coast clones had very different asd sequences which fell into separate lineages in the V. cholerae population. As gene trees drawn from a single gene may not reflect the true topology of the population, we sequenced the mdh (malate dehydrogenase) and hlyA (hemolysin A) genes from representatives of environmental and clinical isolates of V. cholerae and found that the mdh and hlyA sequences from the three pathogenic clones were identical, except for the previously reported 11-bp deletion in hlyA in the sixth-pandemic clone. Identical sequences were obtained, despite average nucleotide differences in the mdh and hlyA genes of 1.52 and 3.25%, respectively, among all the isolates, suggesting that the three pathogenic clones are closely related. To extend these observations, segments of the recA and dnaE genes were sequenced from a selection of the pathogenic isolates, where the sequences were either identical or substantially different between the clones. The results show that the three pathogenic clones are very closely related and that there has been a high level of recombination in their evolution.  (+info)

Insertion of excised IgH switch sequences causes overexpression of cyclin D1 in a myeloma tumor cell. (3/18933)

Oncogenes are often dysregulated in B cell tumors as a result of a reciprocal translocation involving an immunoglobulin locus. The translocations are caused by errors in two developmentally regulated DNA recombination processes: V(D)J and IgH switch recombination. Both processes share the property of joining discontinuous sequences from one chromosome and releasing intervening sequences as circles that are lost from progeny cells. Here we show that these intervening sequences may instead insert in the genome and that during productive IgH mu-epsilon switch recombination in U266 myeloma tumor cells, a portion of the excised IgH switch intervening sequences containing the 3' alpha-1 enhancer has inserted on chromosome 11q13, resulting in overexpression of the adjacent cyclin D1 oncogene.  (+info)

The L1 major capsid protein of human papillomavirus type 11 recombinant virus-like particles interacts with heparin and cell-surface glycosaminoglycans on human keratinocytes. (4/18933)

The L1 major capsid protein of human papillomavirus (HPV) type 11, a 55-kDa polypeptide, forms particulate structures resembling native virus with an average particle diameter of 50-60 nm when expressed in the yeast Saccharomyces cerevisiae. We show in this report that these virus-like particles (VLPs) interact with heparin and with cell-surface glycosaminoglycans (GAGs) resembling heparin on keratinocytes and Chinese hamster ovary cells. The binding of VLPs to heparin is shown to exhibit an affinity comparable to that of other identified heparin-binding proteins. Immobilized heparin chromatography and surface plasmon resonance were used to show that this interaction can be specifically inhibited by free heparin and dextran sulfate and that the effectiveness of the inhibitor is related to its molecular weight and charge density. Sequence comparison of nine human L1 types revealed a conserved region of the carboxyl terminus containing clustered basic amino acids that bear resemblance to proposed heparin-binding motifs in unrelated proteins. Specific enzymatic cleavage of this region eliminated binding to both immobilized heparin and human keratinocyte (HaCaT) cells. Removal of heparan sulfate GAGs on keratinocytes by treatment with heparinase or heparitinase resulted in an 80-90% reduction of VLP binding, whereas treatment of cells with laminin, a substrate for alpha6 integrin receptors, provided minimal inhibition. Cells treated with chlorate or substituted beta-D-xylosides, resulting in undersulfation or secretion of GAG chains, also showed a reduced affinity for VLPs. Similarly, binding of VLPs to a Chinese hamster ovary cell mutant deficient in GAG synthesis was shown to be only 10% that observed for wild type cells. This report establishes for the first time that the carboxyl-terminal portion of HPV L1 interacts with heparin, and that this region appears to be crucial for interaction with the cell surface.  (+info)

Viral gene delivery selectively restores feeding and prevents lethality of dopamine-deficient mice. (5/18933)

Dopamine-deficient mice (DA-/- ), lacking tyrosine hydroxylase (TH) in dopaminergic neurons, become hypoactive and aphagic and die by 4 weeks of age. They are rescued by daily treatment with L-3,4-dihydroxyphenylalanine (L-DOPA); each dose restores dopamine (DA) and feeding for less than 24 hr. Recombinant adeno-associated viruses expressing human TH or GTP cyclohydrolase 1 (GTPCH1) were injected into the striatum of DA-/- mice. Bilateral coinjection of both viruses restored feeding behavior for several months. However, locomotor activity and coordination were partially improved. A virus expressing only TH was less effective, and one expressing GTPCH1 alone was ineffective. TH immunoreactivity and DA were detected in the ventral striatum and adjacent posterior regions of rescued mice, suggesting that these regions mediate a critical DA-dependent aspect of feeding behavior.  (+info)

Locus specificity of polymorphic alleles and evolution by a birth-and-death process in mammalian MHC genes. (6/18933)

We have conducted an extensive phylogenetic analysis of polymorphic alleles from human and mouse major histocompatibility complex (MHC) class I and class II genes. The phylogenetic tree obtained for 212 complete human class I allele sequences (HLA-A, -B, and -C) has shown that all alleles from the same locus form a single cluster, which is highly supported by bootstrap values, except for one HLA-B allele (HLA-B*7301). Mouse MHC class I loci did not show locus-specific clusters of polymorphic alleles. This was considered to be because of either interlocus genetic exchange or the confusing designation of loci in different haplotypes at the present time. The locus specificity of polymorphic alleles was also observed in human and mouse MHC class II loci. It was therefore concluded that interlocus recombination or gene conversion is not very important for generating MHC diversity, with a possible exception of mouse class I loci. According to the phylogenetic trees of complete coding sequences, we classified human MHC class I (HLA-A, -B, and -C) and class II (DRB1) alleles into three to five major allelic lineages (groups), which were monophyletic with high bootstrap values. Most of these allelic groups remained unchanged even in phylogenetic trees based on individual exons, though this does not exclude the possibility of intralocus recombination involving short DNA segments. These results, together with the previous observation that MHC loci are subject to frequent duplication and deletion, as well as to balancing selection, indicate that MHC evolution in mammals is in agreement with the birth-and-death model of evolution, rather than with the model of concerted evolution.  (+info)

Mitotic recombination in the heterochromatin of the sex chromosomes of Drosophila melanogaster. (7/18933)

The frequency of spontaneous and X-ray-induced mitotic recombination involving the Y chromosome has been studied in individuals with a marked Y chromosome arm and different XY compound chromosomes. The genotypes used include X chromosomes with different amounts of X heterochromatin and either or both arms of the Y chromosome attached to either side of the centromere. Individuals with two Y chromosomes have also been studied. The results show that the bulk of mitotic recombination takes place between homologous regions.  (+info)

The prokaryotic beta-recombinase catalyzes site-specific recombination in mammalian cells. (8/18933)

The development of new strategies for the in vivo modification of eukaryotic genomes has become an important objective of current research. Site-specific recombination has proven useful, as it allows controlled manipulation of murine, plant, and yeast genomes. Here we provide the first evidence that the prokaryotic site-specific recombinase (beta-recombinase), which catalyzes only intramolecular recombination, is active in eukaryotic environments. beta-Recombinase, encoded by the beta gene of the Gram-positive broad host range plasmid pSM19035, has been functionally expressed in eukaryotic cell lines, demonstrating high avidity for the nuclear compartment and forming a clear speckled pattern when assayed by indirect immunofluorescence. In simian COS-1 cells, transient beta-recombinase expression promoted deletion of a DNA fragment lying between two directly oriented specific recognition/crossing over sequences (six sites) located as an extrachromosomal DNA substrate. The same result was obtained in a recombination-dependent lacZ activation system tested in a cell line that stably expresses the beta-recombinase protein. In stable NIH/3T3 clones bearing different number of copies of the target sequences integrated at distinct chromosomal locations, transient beta-recombinase expression also promoted deletion of the intervening DNA, independently of the insertion position of the target sequences. The utility of this new recombination tool for the manipulation of eukaryotic genomes, used either alone or in combination with the other recombination systems currently in use, is discussed.  (+info)

Recombination directionality factors (RDFs), or excisionases, are essential players of prophage excisive recombination. Despite the essentially catalytic role of the integrase in both integrative and excisive recombination, RDFs are required to direct the reaction towards excision and to prevent re-integration of the prophage genome when entering a lytic cycle. KplE1, HK620 and numerous (pro)phages that integrate at the same site in enterobacteria genomes (such as the argW tRNA gene) all share a highly conserved recombination module. This module comprises the attL and attR recombination sites and the RDF and integrase genes. The KplE1 RDF was named TorI after its initial identification as a negative regulator of the tor operon. However, it was characterized as an essential factor of excisive recombination. In this study, we designed an extensive random mutagenesis protocol of the torI gene and identified key residues involved in both functions of the TorI protein. We show that, in addition to TorI-TorR
Meiosis is a cell division process that produces haploid gametes from diploid cells. Several important meiotic events take place during prophase of meiosis I, most important being homologous chromosome pairing, meiotic recombination and formation of the synaptonemal complex (SC). These processes assure proper segregation of the homologous chromosomes into the haploid germ cells. Improper segregation of the homologos can cause chromosomal abnormality (aneuploidy), which causes various human disorders, notably mental retardation and pregnancy loss.. This thesis focuses on the relationship between recombination and the formation of SCs, aggregates of SC-related materials (polycomplexes) and recombination enzymes during meiosis. We have investigated SC formation in the absence of recombination, nature of polycomplexes and recombination enzymes in relation to the SCs structures and recombination nodules (RNs) in yeast Saccharomyces cerevisiae.. Studies on yeast mutants suggest that the formation of ...
60125DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 1rkycwgcttt yktrtacnaa stsgb 25225DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 2agccwgcttt yktrtacnaa ctsgb 25325DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 3gttcagcttt cktrtacnaa ctsgb 25425DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 4agccwgcttt cktrtacnaa gtsgb 25525DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 5gttcagcttt yktrtacnaa gtsgb 25625DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 6agcctgcttt tttgtacaaa cttgt 25725DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 7agcctgcttt cttgtacaaa cttgt 25825DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence 8acccagcttt cttgtacaaa gtggt 25925DNAUnknownDescription of Unknown Recombination products oligonucleotide sequence ...
In the nematode Caenorhabditis elegans, recombination suppression in translocation heterozygotes is severe and extensive. We have examined the meiotic properties of two translocations involving chromosome I, szT1(I;X) and hT1(I;V). No recombination was observed in either of these translocation heterozygotes along the left (let-362-unc-13) 17 map units of chromosome I. Using half-translocations as free duplications, we mapped the breakpoints of szT1 and hT1. The boundaries of crossover suppression coincided with the physical breakpoints. We propose that DNA sequences at the right end of chromosome I facilitate pairing and recombination. We use the data from translocations of other chromosomes to map the location of pairing sites on four other chromosomes. hT1 and szT1 differed markedly in their effect on recombination adjacent to the crossover suppressed region. hT1 had no effect on recombination in the adjacent interval. In contrast, the 0.8 map unit interval immediately adjacent to the ...
Author Summary Homologous recombination is an indispensable feature of the mammalian meiotic program and an important mechanism for creating genetic diversity. Despite its central significance, recombination rates vary markedly between species and among individuals. Although recent studies have begun to unravel the genetic basis of recombination rate variation within populations, the genetic mechanisms of species divergence in recombination rate remain poorly characterized. In this study, we show that two closely related house mouse subspecies differ in their genomic recombination rates by ∼30%, providing an excellent model system for studying evolutionary divergence in this trait. Using quantitative genetic methods, we identify eight genomic regions that contribute to divergence in global recombination rate between these subspecies, including large effect loci and multiple loci on the X-chromosome. Our study uncovers novel genomic loci contributing to species divergence in global recombination rate
In Saccharomyces cerevisiae, Rad59 is required for multiple homologous recombination mechanisms and viability in DNA replication-defective rad27 mutant cells. Recently, four rad59 missense alleles were found to have distinct effects on homologous recombination that are consistent with separation-of-function mutations. The rad59-K166A allele alters an amino acid in a conserved α-helical domain, and, like the rad59 null allele diminishes association of Rad52 with double-strand breaks. The rad59-K174A and rad59-F180A alleles alter amino acids in the same domain and have genetically similar effects on homologous recombination. The rad59-Y92A allele alters a conserved amino acid in a separate domain, has genetically distinct effects on homologous recombination, and does not diminish association of Rad52 with double-strand breaks. In this study, rad59 mutant strains were crossed with a rad27 null mutant to examine the effects of the rad59 alleles on the link between viability, growth and the stimulation of
View Notes - Bacterial Recombination from MCB 2000 at University of Florida. BACTERIAL RECOMBINATION Purposes A. Vaccine production (subunit type) B. Production of proteins (growth hormone) C.
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To create this landmark map, Comeron and colleagues generated recombinant advanced intercross lines (RAIL), derived from eight crosses among twelve wild-derived lines. To accurately identify crossover and noncrossover events, haplotype rather than genotype data are required, and Comeron and colleagues use a clever technique to recover haplotypes. RAIL females were individually crossed to D. simulans, and the genomes of single hybrid progeny were sequenced with Illumina technology. Reads mapping to D. simulans were removed bioinformatically to reveal a haploid, meiotically produced D. melanogaster genome. In all, over 100,000 recombination events were localized with kilobase-level precision.. Certainly, this genome-wide recombination map will empower population genetic and molecular evolutionary studies in Drosophila for years to come. However, the sheer number of events catalogued combined with the resolution at which breakpoints could be mapped facilitates a great deal more than quantifying ...
Recombination increases dramatically during meiosis to promote genetic exchange and generate recombinant progeny. Interestingly, meiotic recombination is unevenly distributed throughout genomes, and, as a consequence, genetic and physical map distances do not have a simple linear relationship. Recombination hotspots and coldspots have been described in many organisms and often reflect global features of chromosome structure. In particular, recombination frequencies are often distorted within or outside sex-determining regions of the genome. Here, we report that recombination is elevated adjacent to the mating-type locus (MAT) in the pathogenic basidiomycete Cryptococcus neoformans. Among fungi, C. neoformans has an unusually large MAT locus, and recombination is suppressed between the two |100-kilobase mating-type specific alleles. When genetic markers were introduced at defined physical distances from MAT, we found the meiotic recombination frequency to be ~20% between MAT and a flanking marker at 5,
Recombination hotspots are regions in a genome that exhibit elevated rates of recombination relative to a neutral expectation. The recombination rate within hotspots can be hundreds of times that of the surrounding region. Recombination hotspots result from higher DNA break formation in these regions, and apply to both mitotic and meiotic cells. This appellation can refer to recombination events resulting from the uneven distribution of programmed meiotic double-strand breaks. Meiotic recombination through crossing over is thought to be a mechanism by which a cell promotes correct segregation of homologous chromosomes and repair of DNA damages. Crossing over requires a DNA double-stranded break followed by strand invasion of the homolog and subsequent repair. Initiation sites for recombination are usually identified by mapping crossing over events through pedigree analysis or through analysis of linkage disequilibrium. Linkage disequilibrium has identified more than 30,000 hotspots within the ...
Crossover generated by meiotic recombination is a fundamental event that facilitates meiosis and sexual reproduction. Comparative studies have shown wide variation in recombination rate among species, but the characterization of recombination features between cattle breeds has not yet been performed. Cattle populations in North America count millions, and the dairy industry has genotyped millions of individuals with pedigree information that provide a unique opportunity to study breed-level variations in recombination. Based on large pedigrees of Jersey, Ayrshire and Brown Swiss cattle with genotype data, we identified over 3.4 million maternal and paternal crossover events from 161,309 three-generation families. We constructed six breed- and sex-specific genome-wide recombination maps using 58,982 autosomal SNPs for two sexes in the three dairy cattle breeds. A comparative analysis of the six recombination maps revealed similar global recombination patterns between cattle breeds but with significant
Accessory replicative helicases aid the primary replicative helicase in duplicating protein-bound DNA, especially transcribed DNA. Recombination enzymes also aid genome duplication by facilitating the repair of DNA lesions via strand exchange and also processing of blocked fork DNA to generate structures onto which the replisome can be reloaded. There is significant interplay between accessory helicases and recombination enzymes in both bacteria and lower eukaryotes but how these replication repair systems interact to ensure efficient genome duplication remains unclear. Here, we demonstrate that the DNA content defects of Escherichia coli cells lacking the strand exchange protein RecA are driven primarily by conflicts between replication and transcription, as is the case in cells lacking the accessory helicase Rep. However, in contrast to Rep, neither RecA nor RecBCD, the helicase/exonuclease that loads RecA onto dsDNA ends, is important for maintaining rapid chromosome duplication. Furthermore, RecA
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We have characterized homologous recombination between linear DNA and the bacterial chromosome that depends on λ recombination functions, involves very short homologies, and is very efficient. We examined several parameters to establish a maximal efficiency for phage-mediated recombination with short homologies. Maximal recombination levels are achieved with induction times from 7.5-17.5 min at 42°C, and a homology segment of 40-50 bp. Recombination saturates at a linear DNA substrate concentration of about 300 molecules per cell.. The fact that 30- to 50-bp homologies are able to recombine in vivo opens a vast array of new possibilities for generating recombinant DNA. Several steps normally involved in generating recombinant DNA molecules are eliminated. Restriction enzyme digests are not required to generate DNA fragments, and DNA ligase reactions are not required to join different DNA fragments at novel junctions. PCR amplification followed by electroporation of the linear DNA into cells is ...
October 3, 2004. October 3, 2004 - In a paper published today in the online edition of Nature Genetics, a deCODE-led team of scientists present the results of a large-scale population study linking recombination rate with maternal age and fertility. In the paper, entitled "Recombination rate and reproductive success in humans," the deCODE team establish a novel and significant correlation between recombination - the shuffling of chromosomal material that takes place in the formation of eggs and sperm - and maternal age and fertility. Specifically, the average number of recombinations in eggs that go on to become successful live births tends to increase with the mothers age, and mothers with a higher recombination rate in general also tend to have more children than do those with a lower recombination rate. The authors conclude that the most likely explanation for this phenomenon is that recombination, which is one of the most important mechanisms for generating genetic diversity in ...
Rates of intragenic recombination are suppressed in the vicinity of Ds and Mu1 insertions (23, 34, 40). In addition, Ds insertions are thought to alter the distribution of recombination breakpoints in the otherwise uniformly recombinogenic bz1 locus to create allele-specific hot and cold spots (34). In contrast, a preliminary analysis did not provide any evidence that a Mu1 insertion in the a1 gene alters the distribution of recombination event (23).. In this previous study, the positions of 15 recombination events isolated from the a1-mum2/a1∷rdt heterozygote were physically mapped within the 1.2-kb interval of the a1 gene that is defined by the Mu1 and rdt transposon insertions. All but one of these recombination events resolved within a 377-bp recombination hot spot. Xu et al. (23) compared this distribution of recombination events to those isolated from a directly comparable heterozygote that does not contain the Mu1 insertion in the a1 gene (A1-LC/a1∷rdt). This comparison is appropriate ...
RECOMBINATION plays a crucial role in the molecular evolution of many bacteria, in spite of the clonal nature of bacterial reproduction. Indeed, for a large number of species surveyed in recent studies (Vos and Didelot 2009; Fearnhead et al. 2015), homologous recombination was found to account for a similar or greater number of nucleotide changes than point mutation.. However, many traditional phylogenetic methods (Huelsenbeck and Ronquist 2001; Drummond et al. 2002; Guindon and Gascuel 2003) do not account for recombination. This is regrettable for several reasons. First, ignoring recombination is known to bias phylogenetic analyses in various ways such as by overestimating the number of mutations along branches, artificially degrading the molecular clock hypothesis, and introducing apparent exponential population growth (Schierup and Hein 2000). Second, much of modern computational phylogenetics extends beyond the inference of phylogenetic relationships and instead focuses on the parametric ...
In viruses, recombination may allow foreign genes to be acquired or may create a composite genome through recombination between different virus variants. The ability to identify a recombinant virus and the positions where recombination occurred is only as certain as the identification of the component parental viral genomes from which it was generated. Recombination detection thus shares many elements and is ultimately dependent on evolutionary reconstructions and, most importantly, on methods for the delineation of separate phylogenetic groups. The structure of the 5 untranslated region (5 UTR) of picornaviruses provides a further example of modular exchange through recombination during the evolution of separate genera within the picornavirus family. Members of the same picornavirus genus show conserved gene order and content, and over the much shorter evolutionary time scale in which species and serotypes developed, gene exchange is best documented as homologous recombination events. One of the
Meiotic recombination hotspots control the frequency and distribution of Spo11 (Rec12)-initiated recombination in the genome. Recombination occurs within and is regulated in part by chromatin structure, but relatively few of the many chromatin remodeling factors and histone posttranslational modifications (PTMs) have been interrogated for a role in the process. We developed a chromatin affinity purification and mass spectrometry-based approach to identify proteins and histone PTMs that regulate recombination hotspots. Small (4.2 kbp) minichromosomes (MiniCs) bearing the fission yeast ade6-M26 hotspot or a basal recombination control were purified approximately 100,000-fold under native conditions from meiosis; then, associated proteins and histone PTMs were identified by mass spectrometry. Proteins and PTMs enriched at the hotspot included known regulators (Atf1, Pcr1, Mst2, Snf22, H3K14ac), validating the approach. The abundance of individual histones varied dynamically during meiotic progression in
Genetic recombination is the production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from the parents to the offspring. Most recombination is naturally occurring. During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a section of genetic material is copied from one chromosome to another, without the donating chromosome being changed) (see SDSA pathway in Figure); or by the breaking and rejoining of DNA strands, which forms new molecules of DNA (see DHJ pathway in Figure). Recombination may also occur during mitosis in eukaryotes where it ordinarily involves the two sister chromosomes formed after chromosomal replication. In this case, new combinations of ...
In yeast meiosis, ascosporal colonies are sometimes sectored for a marker--i.e., half the colony has one allele and half has the other. This is interpreted as replicative resolution of heteroduplex DNA (hDNA) formed as a recombination intermediate. We have looked for similar evidence of hDNA formation during mitotic recombination between two repeated sequences on the same chromosome. The two repeats, an ochre suppressor and a wild-type tRNA gene, are separated by plasmid DNA and the URA3 marker. Recombination between the repeats excises the URA3 gene and one copy of the repeat, leaving either the wild-type tRNA or the suppressor on the chromosome. A red/white color assay is used to distinguish between the two. We find that some colonies that have lost the URA3 gene are sectored for the suppressor. This suggests that hDNA is formed across the anticodon during the recombination event and then resolved by replication. The disruption of either of two genes involved in recombination and repair, RAD1 and
[email protected] research • lab members • publications. My lab is active in three somewhat related research areas: 1) the mechanism of mitotic recombination, 2) the genetic regulation of genome stability, and 3) genetic instability associated with interstitial telomeric sequences. Almost all of our studies are done using the yeast Saccharomyces cerevisiae.. Mechanism of mitotic recombination. Mitotic recombination, an important mechanism for the repair of DNA damage, is less well characterized than meiotic recombination. One difficulty is that mitotic recombination events are 104-fold less frequent than meiotic recombination events. We developed a greatly improved system for identifying and mapping mitotic crossovers at 1-kb resolution throughout the genome. This system uses DNA microarrays to detect loss of heterozygosity (LOH) resulting from mitotic crossovers. We identified motifs associated with high levels of spontaneous mitotic recombination. In particular, we demonstrated that a ...
The emergence of novel pathogenic organisms due to the acquisition of virulence determinants from bacteriophages has generated significant interest in the pathways responsible for genomic rearrangements. Phageλ encodes its own recombination system, the Red system, comprising Exo, β and γ proteins. In addition,λ encodes another recombinase, Orf, which participates in the initial stages of genetic exchange and supplies a frmction equivalent to that of the Escherichia coli RecFOR proteins. This thesis focuses on determining the function of Orf in phage and bacterial recombination pathways by analysing its impact on recombinases encoded by λ and E. coli. Experiments revealed that Orf interacts with bacterial and phage recombination proteins in the initial exchange step of recombination, modulating the activities of both Exo and RecA. Orf, along with β, attenuates the 5-3 exonuclease activity of Exo, a feature that depends largely on the ability of Orf to bind DNA. Orf also facilitates ...
Parasites and hosts are involved in a continuous coevolutionary process leading to genetic changes in both counterparts. To understand this process, it is necessary to track host responses, one of which could be an increase in sex and recombination, such as is proposed by the Red Queen hypothesis. In this theoretical framework, the inducible recombination hypothesis states that B-chromosomes (genome parasites that prosper in natural populations of many living beings) elicit an increase in host chiasma frequency that is favoured by natural selection because it increases the proportion of recombinant progeny, some of which could be resistant to both B-chromosome effects and B-accumulation in the germline. We have found a clear parallelism between host recombination and the evolutionary status of the B-chromosome polymorphism, which provides explicit evidence for inducible recombination and strong support for the Red Queen hypothesis.. ...
Despite their importance to successful meiosis and various evolutionary processes, meiotic recombination rates sometimes vary within species or between closely related species. For example, humans and chimpanzees share virtually no recombination hotspot locations in the surveyed portion of the genom …
Although DNA is surprisingly fluid, there are enzymes that mediate recombination--by initiating DNA binding, strand invasion, and stabilizing ssDNA intermediates. Also, of important note, is that organisms have varying degrees of recombination levels. A classical example occurs within the Mycobacteria. Mycobacterium smegmatis has relatively low levels of illegitimate recombination (IR), while M. tuberculosis is notorious for high levels of IR compared to homologous recombination. This raises a question that can be phrased in a few ways. "What enzymes are responsible for IR?" or perhaps, "What enzymes for homologous recombination are lacking ...
Lien vers Pubmed [PMID] - 15218022. J. Biol. Chem. 2004 Aug;279(35):36625-32. By frequently rearranging large regions of the genome, genetic recombination is a major determinant in the plasticity of the human immunodeficiency virus type I (HIV-1) population. In retroviruses, recombination mostly occurs by template switching during reverse transcription. The generation of retroviral vectors provides a means to study this process after a single cycle of infection of cells in culture. Using HIV-1-derived vectors, we present here the first characterization and estimate of the strength of a recombination hot spot in HIV-1 in vivo. In the hot spot region, located within the C2 portion of the gp120 envelope gene, the rate of recombination is up to ten times higher than in the surrounding regions. The hot region corresponds to a previously identified RNA hairpin structure. Although recombination breakpoints in vivo cluster in the top portion of the hairpin, the bias for template switching in this same ...
Meiotic recombination is initiated by DNA double-strand breaks (DSBs) created by the topoisomerase-like protein Spo11. During DSB formation, Spo11 becomes covalently attached to the 5 DSB ends. Removal of Spo11 is essential to repair the DSB by homologous recombination. Spo11 is removed endonucleolytically creating short-lived Spo11-oligonucleotide products. Here I demonstrate that: 1. Spo11-oligonucleotide products are not detected in recombination mutants believed to be defective in meiotic DSB formation. 2. When DSB repair is delayed, Spo11-oligonucleotides persist for longer. 3. Processing of Spo11-DSB ends to create Spo11-oligonucleotides is largely dependent on Mec1 and Tel1 activity. In the process of investigating Spo11-oligonucleotide degradation, it was observed that a mutant defective in both the meiotic recombination checkpoint and in DSB repair failed to accumulate the expected level of DSBs. Work described here leads to the proposal of a DSB feedback mechanism that functions ...
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Recombination raises during meiosis to market genetic exchange and generate recombinant progeny dramatically. hereditary markers were released at described physical ranges from we discovered the meiotic recombination rate of recurrence to become ~20% between and a flanking marker at 5, 10, 50, or 100 kilobases from the proper border. As a total result, the physical/hereditary map percentage in the areas adjacent to can be distorted ~10- to 50-collapse set alongside the genome-wide normal. Moreover, recombination frequently occurred on both family member edges of and bad disturbance between crossovers was observed. heterozygosity had not been required for improved recombination, implying that process CALNA2 isnt because of a physical distortion from both non-paired alleles and may also happen during same-sex mating. Series analysis exposed a 68550-75-4 supplier relationship between high G + C content material and these hotspot areas. We hypothesize that the current presence of recombinational ...
I have posted a few times before about a new group bionet.molbio.recombination that I will be proposing soon.... Here is the rough proposal... if you have any comments please send them!!!! Start----------- Proposal to establish RECOMBINATION/bionet.molbio.recombination Proposed USENET name: bionet.molbio.recombination (unmoderated) Proposed mailing list name: RECOMBINATION Proposed e-mail addresses: recom at net.bio.net recom at daresbury.ac.uk Discussion leaders: Graham Dellaire, e-mail: popa0206 at po-box.mcgill.ca (b2xe at musicb.mcgill.ca) Department of Medicine (Div. of Exp. Medicine), McGill Univeristy, Montreal, Quebec, Canada George Szatmari, e-mail: szat at ere.umontreal.ca Tentatively Denis Cournoyer (Mcgill Experimental Medicine) (gene therapy) Terry Chow (McGill): e-mail MDTY at Musica.mcgill.ca (mammalian genetics) Charter: The purpose of the RECOMBINATION newsgroup is to provide a proper forum for the discussion of issues pertaining and involving recombination of DNA or RNA, in its ...
Whereas the core homologous-recombination machinery is conserved between yeast and humans, it is now clear that additional important homologous-recombination proteins, such as BRCA1 and BRCA2, are present only in mammalian cells. Germline mutations in the BRCA1 and BRCA2 genes were first identified because they predispose carriers to breast cancer [17]. Early on, associations between both BRCA proteins and human Rad51 were demonstrated, suggesting a link between homologous recombination and the BRCA proteins [17]. The involvement of the BRCA proteins in homologous recombination has now been firmly established by recent experiments from a number of laboratories.. The involvement of mouse Brca1 in homologous recombination was established by the Jasin [18] and Koller [19] laboratories. They used homologous gene-targeting assays to measure the efficiency of homologous recombination. They found that gene targeting in Brca1-deficient mouse embryonic stem cells was reduced by more than 20-fold compared ...
Molecular models of meiotic recombination have evolved over the years as relevant evidence accumulated. A major incentive for developing a fundamental understanding of the mechanism of meiotic recombination is that such understanding is crucial for solving the problem of the adaptive function of sex, a major unresolved issue in biology. A recent model that reflects current understanding was presented by Anderson and Sekelsky,[7] and is outlined in the first figure in this article. The figure shows that two of the four chromatids present early in meiosis (prophase I) are paired with each other and able to interact. Recombination, in this version of the model, is initiated by a double-strand break (or gap) shown in the DNA molecule (chromatid) at the top of the first figure in this article. However, other types of DNA damage may also initiate recombination. For instance, an inter-strand cross-link (caused by exposure to a cross-linking agent such as mitomycin C) can be repaired by HRR. As ...
Recombination enhances the adaptive potential of organisms by allowing genetic variants to be tested on multiple genomic backgrounds. Its distribution in the genome can provide insight into the evolutionary forces that underlie traits, such as the emergence of pathogenicity. Here, we examined landscapes of realized homologous recombination of 500 genomes from ten bacterial species and found all species have hot regions with elevated rates relative to the genome average. We examined the size, gene content, and chromosomal features associated with these regions and the correlations between closely related species. The recombination landscape is variable and evolves rapidly. For example in Salmonella, only short regions of around 1 kb in length are hot whereas in the closely related species Escherichia coli, some hot regions exceed 100 kb, spanning many genes. Only Streptococcus pyogenes shows evidence for the positive correlation between GC content and recombination that has been reported for several
Homologous recombination is a process that occurs within the chromosome and which allows one piece of DNA to be exchanged for another piece. It is a cellular mechanism that is probably part of the normal process cells use to repair breaks in their chromosomes. Homologous recombination A modified version of the target gene replaces it in the chromosome. The target gene is removed and degraded. In this example, the gene is modified by insertion of an antibiotic resistance gene, which both inactivates the gene and allows efficient selection of transformed cells. requires that the pieces of DNA undergoing recombination be almost identical (homologous) in sequence. In addition, sequences on either side of the target should be identical, to promote more efficient targeting and recombination.. By constructing a sequence that is homologous to a target sequence (such as a gene), laboratory researchers can replace one of the cells own copies of a particular gene with a copy that has been altered in some ...
Methods for evolving recombinase protein homologues and RecA/VirE2 fusion proteins which complement VirE2 deficient Agrobacterium are provided. The use of recombinase protein homologues and RecA/VirE2 fusion proteins in the context of Agrobacterium mediated transformation are provided. Methods for producing transgenic organisms by homologous recombination using evolved recombinase proteins and Agrobacterium strains which express recombinase protein homologues or RecA/VirE2 fusion proteins are provided. Transgenic cells and organisms which have integrated an exogenous DNA sequence into a predetermined site in their genome are provided.
Eukaryotic organisms maintain stable genomes despite the presence of repeated DNA sequences and efficient homologous recombination. The absence of frequent deletions and translocations due to exchange between repeats, particularly in meiosis where recombination is elevated, suggests the existence of mechanisms to suppress such recombination. Indeed, the amount of meiotic recombination per unit length DNA falls dramatically as the size and repetitive DNA content of eukaryotic genomes increases. For example, although human cells contain ∼150 times more DNA per haploid genome than yeast, both species exhibit similar numbers of reciprocal exchanges per meiosis (Lewin, 1990). The basis for this decline in recombination frequencies is not well understood, but may be explained by such diverse mechanisms as changes in chromosome compaction and altered distribution and/or reduced frequency of recombination initiation sites in the genome.. Our laboratory has investigated the pathways of recombination in ...
BACKGROUND: Although homologous recombination affects the efficacy of selection in populations, the pattern of recombination rate evolution and its effects on genome evolution across plants are largely unknown. Recombination can reduce genome size by enabling the removal of LTR retrotransposons, alter codon usage by GC biased gene conversion, contribute to complex histories of gene duplication and loss through tandem duplication, and enhance purifying selection on genes. Therefore, variation in recombination rate across species may explain some of the variation in genomic architecture as well as rates of molecular evolution. We used phylogenetic comparative methods to investigate the evolution of global meiotic recombination rate in angiosperms and its effects on genome architecture and selection at the molecular level using genetic maps and genome sequences from thirty angiosperm species. RESULTS: Recombination rate is negatively correlated with genome size, which is likely caused by the ...
Mechanism and Control of Meiotic Recombination. We study homologous recombination and chromosome structural changes that occur during meiosis, using budding yeast as a model system. Recombination, and in particular the crossover products of recombination, are essential for proper chromosome segregation during meiosis. Chromosome mis-segregation caused by defects in meiotic recombination leads to chromosome imbalance in gametes, and these chromosome imbalances are a leading cause of infertility and birth defects in modern human populations. We aim to describe the molecular steps of meiotic recombination, and how they are regulated in parallel with changes in chromosome structure and with cell cycle transitions that occur during meiosis. Because meiosis is an excellent model system to study homologous recombination, our findings also have provided insight into mechanisms by which DNA damage is repaired and genome integrity is maintained during the mitotic cell cycle.. Meiotic recombination ...
Mph1 is a member of the conserved FANCM family of DNA motor proteins that play key roles in genome maintenance processes underlying Fanconi anemia, a cancer predisposition syndrome in humans. Here, we identify Mte1 as a novel interactor of the Mph1 helicase in Saccharomyces cerevisiae. In vitro, Mte1 (Mph1-associated telomere maintenance protein 1) binds directly to DNA with a preference for branched molecules such as D loops and fork structures. In addition, Mte1 stimulates the helicase and fork regression activities of Mph1 while inhibiting the ability of Mph1 to dissociate recombination intermediates. Deletion of MTE1 reduces crossover recombination and suppresses the sensitivity of mph1Δ mutant cells to replication stress. Mph1 and Mte1 interdependently colocalize at DNA damage-induced foci and dysfunctional telomeres, and MTE1 deletion results in elongated telomeres. Taken together, our data indicate that Mte1 plays a role in regulation of crossover recombination, response to replication ...
A molecular clone containing the complete sequence of a mitochondrial circular plasmid-like DNA (the R plasmid) isolated from the date-palm variety V3DP was used as a probe in Southern analyses of mitochondrial DNA prepared from other varieties. Another circular structure (the S plasmid) was detected in some of these varieties, and sequenced from variety V2DP. It appears that the R plasmid could have arisen from the S plasmid by an intermolecular recombination event at a set of 26-bp imperfect short direct repeats.
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The tyrosine family of recombinases produces two smaller DNA circles when acting on circular DNA harboring two recombination sites in head-to-tail orientation. If the substrate is supercoiled, these circles can be unlinked or form multiply linked catenanes. The topological complexity of the products varies strongly even for similar recombination systems. This dependence has been solved here. Our computer simulation of the synapsis showed that the bend angles, phi, created in isolated recombination sites by protein binding before assembly of the full complex, determine the product topology. To verify the validity of this theoretical finding we measured the values of phi for Cre/loxP and Flp/FRT systems. The measurement was based on cyclization of the protein-bound short DNA fragments in solution. Despite the striking similarity of the synapses for these recombinases, action of Cre on head-to-tail target sites produces mainly unlinked circles, while that of Flp yields multiply linked catenanes. In full
Genetic recombination during meiosis functions to increase genetic diversity, promotes elimination of deleterious alleles, and helps assure proper segregation of chromatids. Mammalian recombination events are concentrated at specialized sites, termed hotspots, whose locations are determined by PRDM9, a zinc finger DNA-binding histone methyltransferase. Prdm9 is highly polymorphic with most alleles activating their own set of hotspots. In populations exhibiting high frequencies of heterozygosity, questions remain about the influences different alleles have in heterozygous individuals where the two variant forms of PRDM9 typically do not activate equivalent populations of hotspots. We now find that, in addition to activating its own hotspots, the presence of one Prdm9 allele can modify the activity of hotspots activated by the other allele. PRDM9 function is also dosage sensitive; Prdm9+/- heterozygous null mice have reduced numbers and less active hotspots and increased numbers of aberrant germ cells. In
This paper proposes a model for the evolution of recombination. The model is based on the notion that when a species (say species 1) interacts with other antagonistic species, species 1 will act as a selective force on them, favouring antagonists best able to destroy its most frequent phenotypes. Only if the progeny of these phenotypes are different from their parents are they able to escape the full force of selected antagonists. A deterministic haploid genetic model with two linked loci and a third unlinked recombination-modifying locus is constructed, using frequency-dependent selection with time delay, to describe the effects of antagonists. Analysis of the model shows that a modifier mutant causing recombination usually starts to spread into a population without recombination, and under certain conditions can spread even if there is already some recombination in the population. The relevance of these results to observations of recombination in the natural world is discussed. ...
Meiosis is a special division during which a cell undergoes two sequential rounds of chromosome segregation with no intervening DNA replication, to generate gamete cells with half the original chromosomal complement. During the first meiotic division (meiosis I), recombination among homologous chromosomes generates novel genetic combinations that play an important role in evolution and breeding. Crossovers persist as cytologically visible chiasmata until homologues segregate in metaphase I and are important for ensuring balanced segregation of homologues [1]. Thus the evolutionarily important effects of recombination and allele shuffling are intimately tied to the physical workings of meiotic chromosome segregation and the maintenance of genome integrity over generations.. Meiotic recombination is an elaborate process, involving numerous steps that take place over the course of many hours (e.g. [2]). Recombination is essentially a DNA repair process that relies on initial programmed double ...
The biochemical processes of DNA repair, replication and recombination compete for the same substrate, the DNA molecule. This competition is natural, as each process requires the same template. In order to resolve possible conflicts between these processes, when they take place on a particular stretch of DNA, certain crosstalk is expected. The complexity is additionally increased by the existence of another DNA dependent process, which occurs in all phases of the cell cycle: transcription.. This thesis aims to investigate the link between transcription inhibition and homologous recombination, especially in the context of UV-induced DNA damage. The results show that the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) induces homologous recombination. The DNA damage caused by UVC irradiation is repaired mainly via nucleotide excision repair, however, it is also known to trigger recombinational repair. In the presence of UV-induced damage, transcription inhibition by ...
Homologous recombination utilizing hosts own recombination machinery is widely used for genome engineering. More specifically, a plasmid that carries homologous arms to the upstream and downstream areas of target gene(s), is introduced into the host. In order to select for a double crossover event (gene deletion), a positive selection (such as antibiotic resistance cassettes) or combination with a negative selection (such as mazF [84] or pyrE [85]) is used. Other variant methods that rely on homologous recombination also include Allele-Coupled Exchange (ACE) [86], Triple crossover [87] and scar-less, marker-less knockout or knock-in using two negative selection markers (C. thermocellum), detailed information has recently been reviewed [88]. In some instances, specific DNA sequences which can be recognized by site-specific recombinases, flanking the antibiotic resistance cassettes were introduced into the chromosome at the same time during the double crossover event. The antibiotic resistance ...
They are also used in DNA repair and genetic recombination.[120] Topoisomerases and helicases. Topoisomerases are enzymes with ... Non-homologous recombination can be damaging to cells, as it can produce chromosomal translocations and genetic abnormalities. ... Recombination allows chromosomes to exchange genetic information and produces new combinations of genes, which increases the ... The recombination reaction is catalyzed by enzymes known as recombinases, such as RAD51.[132] The first step in recombination ...
... and genetic recombination[edit]. Meiosis results in a random segregation of the genes that each parent ... In addition, it is thought by some,[40] that a long-term advantage of out-crossing in nature is increased genetic variability ... One is that it evolved from prokaryotic sex (bacterial recombination) as eukaryotes evolved from prokaryotes.[6] The other is ... Otto, S.P; Gerstein, A.C (2006). "Why have sex? The population genetics of sex and recombination". Biochemical Society ...
Genetic Recombination *^ a b c Smith, George P. (1976-01-01). "Evolution of Repeated DNA Sequences by Unequal Crossover". ... It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a ... Due to this genetic recombination, the offspring have a different set of alleles and genes than their parents do. In the ... This leads to the notion of "genetic distance", which is a measure of recombination frequency averaged over a (suitably large) ...
This process is known as genetic recombination. The rate of recombination of two discrete loci corresponds to their physical ... "Genetic Recombination and Gene Mapping , Learn Science at Scitable". www.nature.com. Retrieved 2016-04-10. Single, Richard M.; ... Through recombination, daughter cells have the greatest amount of genetic diversity. (Click Here for a video tutorial ... "Genetic Recombination and Gene Mapping , Learn Science at Scitable". www.nature.com. Retrieved 2016-04-10. Palhares, Alessandra ...
In sexual populations, the process of genetic recombination allows the genomes of the progeny to be different from the genomes ... Evolution of sexual reproduction Genetic hitchhiking Mutational meltdown Hill-Robertson effect Muller HJ (1932). "Some genetic ... This results in an eventual accumulation of mutations known as genetic load. In theory, the genetic load carried by asexual ... Because Muller's ratchet relies on genetic drift, it turns faster in smaller populations and it is thought to set limits to the ...
... and genetic recombinationEdit. Meiosis results in a random segregation of the genes that each parent contributes ... In addition, it is thought by some,[32] that a long-term advantage of out-crossing in nature is increased genetic variability ... Otto, SP; Gerstein, AC (2006). "Why have sex? The population genetics of sex and recombination". Biochem Soc Trans. 34 (4): 519 ... Abbott, RJ; Gomes, MF (1989). "Population genetic structure and outcrossing rate of Arabidopsis thaliana (L.) Heynh". Heredity ...
Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule ... Umene K. Mechanism and application of genetic recombination in herpesviruses. Reviews in Medical Virology. 1999;9(3):171-82. ... Some viruses undergo a lysogenic cycle where the viral genome is incorporated by genetic recombination into a specific place in ... long molecules that carry genetic information; (ii) a protein coat, called the capsid, which surrounds and protects the genetic ...
Recombination. Further information: Genetic recombination. Two RNA genomes are encapsidated in each HIV-1 particle (see ... Viral recombination produces genetic variation that likely contributes to the evolution of resistance to anti-retroviral ... This form of recombination is known as copy-choice. Recombination events may occur throughout the genome. Anywhere from two to ... "High frequency of genetic recombination is a common feature of primate lentivirus replication". Journal of Virology. 80 (19): ...
Genetic mosaics can also be created through mitotic recombination. Such mosaics were originally created by irradiating flies ... Mitotic recombination[edit]. One basic mechanism which can produce mosaic tissue is mitotic recombination or somatic crossover ... "Genetic mosaics in animals and man". pp27-129, in Stern, C. Genetic Mosaics and Other Essays. Harvard University Press, ... Curt Stern demonstrated that genetic recombination, normal in meiosis, can also take place in mitosis.[21][22] When it does, it ...
Margulis, Lynn; Sagan, Dorion (1986). Origins of sex: three billion years of genetic recombination. The Bio-origins series. New ...
During this time, there can be genetic recombination events. Parts of the chromosome 2 DNA gained from one parent (red) will ... Genetic studies of the fruit fly Drosophila have revealed several genes that are required for the formation of multinucleated ... as well as increase in genetic material (G2 phase) following the replication during S phase.[1] This is not to be confused with ...
Males do not show meiotic recombination, facilitating genetic studies.. *Recessive lethal "balancer chromosomes" carrying ... History of use in genetic analysis[edit]. Alfred Sturtevant's Drosophila melanogaster genetic linkage map: This was the first ... Genetic markers[edit]. Genetic markers are commonly used in Drosophila research, for example within balancer chromosomes or P- ... Classic genetic mutations[edit]. Drosophila genes are traditionally named after the phenotype they cause when mutated. For ...
Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis in ascospores. In its ... Many types of virus are capable of genetic recombination. When two or more individual viruses of the same type infect a cell, ... Cellular aggregation mediates chromosomal marker exchange and genetic recombination with high frequency. Cellular aggregation ... that the genetic code is a triplet code,[40] and that gene expression is regulated by specific genetic processes.[41] Jacques ...
Moreover, cells that do not integrate any of the genetic material test negative for both genes and therefore die as a result of ... The chances of a successful recombination event are relatively low, so the majority of altered cells will have the new sequence ... Wolfer DP, Crusio WE, Lipp HP (July 2002). "Knockout mice: simple solutions to the problems of genetic background and flanking ... By the natural process of homologous recombination some of the electroporated stem cells will incorporate the new sequence with ...
"Genetic Recombination , Learn Science at Scitable". www.nature.com. Retrieved 2015-11-13. Yamada, Kazuhiro; Ariyoshi, Mariko; ... Branch migration is the second step of genetic recombination, following the exchange of two single strands of DNA between two ... present during recombination. The ions determine which structure the Holliday junction will adopt, as they play a stabilizing ... influencing the degree of which the genetic material is exchanged. Branch migration can also be seen in DNA repair and ...
Synthetic genetic array Saccharomyces cerevisiae Ascus Homologous recombination Genetic recombination Ascospore Perkins, D.D. ( ... Genetic Recombination. New York: Wiley; 1982. ISBN 978-0471102052 Yeast Protocols: Methods in Cell and Molecular Biology, Ivor ... These studies have proven central to understanding the mechanism of meiotic recombination, which in turn is a key to ... The use of tetrads in fine-structure genetic analysis is described in the articles Neurospora crassa and Gene conversion. ...
Some insulins are biosynthetic products produced using genetic recombination techniques; formerly, cattle or pig insulins were ... Main article: Genetic causes of diabetes mellitus type 1. Type 1 diabetes is a disease that involves many genes. The risk of a ... Pociot, F; Lernmark, Å (4 June 2016). "Genetic risk factors for type 1 diabetes". The Lancet. 387 (10035): 2331-39. doi:10.1016 ... The cause of type 1 diabetes is unknown.[4] However, it is believed to involve a combination of genetic and environmental ...
Three Billion Years of Genetic Recombination" (book). 1. Yale University Press. ISBN 978-0-300-04619-9.. ... UVB causes thymine base pairs next to each other in genetic sequences to bond together into thymine dimers, a disruption in the ... This leads to frameshifting during genetic replication and protein synthesis, usually killing the cell. Before formation of the ... The few that survived had developed enzymes that monitored the genetic material and removed thymine dimers by nucleotide ...
Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis in Neurospora ascospores ... 1982). Genetic Recombination. Wiley, New York ISBN 978-0471102052 Leslie JF, Raju NB (December 1985). "Recessive mutations from ... An understanding of recombination is relevant to several fundamental biologic problems, such the role of recombination and ... of the molecular mechanism of recombination is discussed in the Wikipedia articles Gene conversion and Genetic recombination. ...
... particularly the analysis of the molecular mechanism of genetic recombination. When a wild type (+) strain is mated with a ... The natural habitat of the three species of Sordaria that have been the principal subjects in genetic studies is dung of ... These species share a number of characteristics that are advantageous for genetic studies. They all have a short life cycle, ... asci). The retention of the products of an individual meiosis in an individual ascus has facilitated certain kinds of genetic ...
Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst species (or ... multilevel selection and indirect genetic effects on response to genetic selection". Journal of Evolutionary Biology. 21 (5): ... Jablonka, E.; Lamb, M. (2005). Evolution in four dimensions: Genetic, epigenetic, behavioural, and symbolic. MIT Press. ISBN 0- ... Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information.[2 ...
Genetic recombination India portal Biology portal "Brief Profile of the Awardee". Shanti Swarup Bhatnagar Prize. 2016. ... Pandey's researches are focused on genetic recombination and his studies on young rats revealed the presence of a DNA ... He proposed that this presence in the prolymphocytes influences the rearrangement and recombination of genes in vertebrates. ...
Induced meiotic recombination". Mutat. Res. 12 (3): 269-79. doi:10.1016/0027-5107(71)90015-7. PMID 5563942. Bleuyard JY, ... Schewe MJ, Suzuki DT, Erasmus U (July 1971). "The genetic effects of mitomycin C in Drosophila melanogaster. II. ... In the fruit fly Drosophila melanogaster, exposure to mitomycin C increases recombination during meiosis, a key stage of the ... In the plant Arabidopsis thaliana, mutant strains defective in genes necessary for recombination during meiosis and mitosis are ...
Lederberg J (1955). "Genetic recombination in bacteria". Science. 122 (3176): 920. doi:10.1126/science.122.3176.920. PMID ... Wollman EL, Jacob F, Hayes W (1956). "Conjugation and genetic recombination in Escherichia coli K-12". Cold Spring Harbor ... In analogy with fertilization and meiosis of higher organisms, he proposed that all of the genetic material was transferred but ... If mating terminated before the prophage was transferred, phage was not produced, and recombination proceeded in the zygote. ...
... s are genetic recombination enzymes. DNA recombinases are widely used in multicellular organisms to manipulate the ...
While schizophrenia is widely believed to be multifactorially genetic by biopsychiatrists, no characteristic genetic markers ... and the apparent QTL effect at a marker will be smaller than the true QTL effect as a result of recombination between the ... then there is a strong chance that the disease is genetic[citation needed] and that the patient will also be a genetic carrier ... If a genetic cause is suspected and little else is known about the illness, then it remains to be seen exactly how many genes ...
Although a number of steps in recombination have been well characterized, many other details about this process remain ... DNA recombination occurs frequently in many different cell types, and it has important implications for genomic integrity, ... Although common, genetic recombination is a highly complex process. It involves the alignment of two homologous DNA strands ( ... DNA recombination involves the exchange of genetic material either between multiple chromosomes or between different regions of ...
Animations showing several models of homologous recombination The Holliday Model of Genetic Recombination Genetic recombination ... ordinarily precedes genetic recombination. Genetic recombination is catalyzed by many different enzymes. Recombinases are key ... In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from ... V(D)J recombination in organisms with an adaptive immune system is a type of site-specific genetic recombination that helps ...
Scientists in Rochester have discovered a gene in fruit flies that is responsible for the evolution of these recombination ... Genetic recombination is vital to natural selection, yet some species display far more crossover than others. ... The importance of genetic recombination. "Natural selection works best when theres a diversity of genotypes to act upon," says ... Genetic recombination is vital to natural selection, yet some species display far more crossover than others. Scientists in ...
GENETIC RECOMBINATION IN SYNCHRONIZED CULTURES OF SACCHAROMYCES CEREVISIAE. Rochelle E. Esposito. Genetics June 1, 1968 vol. 59 ... GENETIC RECOMBINATION IN SYNCHRONIZED CULTURES OF SACCHAROMYCES CEREVISIAE. Rochelle E. Esposito. Genetics June 1, 1968 vol. 59 ... GENETIC RECOMBINATION IN SYNCHRONIZED CULTURES OF SACCHAROMYCES CEREVISIAE. Rochelle E. Esposito. Genetics June 1, 1968 vol. 59 ... GENETIC RECOMBINATION IN SYNCHRONIZED CULTURES OF SACCHAROMYCES CEREVISIAE Message Subject (Your Name) has forwarded a page to ...
... or chromosomal crossover is when chromosomes or regions of the same chromosome ... The main function of genetic recombination is to incorporate both genes of the male and female gamete, to boost genetic ... Prokaryotic Genetic Recombination and Types of Operons. Discuss the two different types of operons found in bacterial genomes ( ... Diversity from genetic recombination can increase the adaptability of organisms to survive in changing environment by ...
Types of recombination. Genetic recombination is initiated by nicks or breaks between base pairs in the donor dsDNA. There are ... Homologous Recombination from a Genetic Perspective. Recombination involves the cutting and covalent joining of DNA sequences. ... The genetic perspective of recombination is important because it has many practical implications, such as genetic mapping. ... a genetic selection is typically required to find a specific recombination event in vivo.) *The co-inheritance of two genetic ...
Genetic Mapping and Genomic Selection Using Recombination Breakpoint Data. Shizhong Xu. Genetics November 1, 2013 vol. 195 no. ... Genetic Mapping and Genomic Selection Using Recombination Breakpoint Data. Shizhong Xu. Genetics November 1, 2013 vol. 195 no. ... Genetic Mapping and Genomic Selection Using Recombination Breakpoint Data. Shizhong Xu. Genetics November 1, 2013 vol. 195 no. ... Genetic Mapping and Genomic Selection Using Recombination Breakpoint Data Message Subject (Your Name) has forwarded a page to ...
Mismatch repair proteins: key regulators of genetic recombination.. Surtees JA1, Argueso JL, Alani E. ... MMR proteins also act during genetic recombination in steps that include repairing mismatches in heteroduplex DNA, modulating ... Second, we will examine the role of MMR proteins in repressing homeologous recombination, i.e. recombination between divergent ... In this review we will, first, discuss roles for MMR proteins in repairing mismatches that occur during recombination, ...
The recombination frequency between gene "Q" and gene "Z" is found to be 23.5%. The recombination frequency between "Q" and a ... D is true because the recombination frequency between R and Z (13.5%) , the recombination frequency between R and Q (10%). ... third gene "R" is 10%. The frequency of recombination between "Z" and "R" is 13.5%. Which one of the following is NOT true ...
DNA »DNA sequences »chromosomes »fruit flies »genes »genetic elements »genetic material »melanogaster »natural selection ... Further reports about: , DNA , DNA sequences , chromosomes , fruit flies , genes , genetic elements , genetic material , ... Scientists have long recognized that the exchange of genetic material by crossing over--known as recombination--is vital to ... Rochester scientists discover gene controlling genetic recombination rates. 23.04.2018. Genetics is a crapshoot. During sexual ...
... recombination genetic include Recombineering Homologous Recombination Constructs in Drosophila. ... Genetic conjugation; Genetic transduction; or mixed infection of viruses. Recombineering Homologous Recombination Constructs in ... Recombination, Genetic: Production of new arrangements of DNA by various mechanisms such as assortment and segregation, ...
Genetic recombination before commitment to meiosis in Saccharomyces. Proc. Nat. Acad. Sci. U.S.A. in press.Google Scholar ... Esposito R.E., Plotkin D.J., Esposito M.S. (1974) The Relationship between Genetic Recombination and Commitment to Chromosomal ... The Relationship between Genetic Recombination and Commitment to Chromosomal Segregation at Meiosis. ... Genic Recombination Sporulation Medium Intragenic Recombination Meiotic Segregation Meiotic Product These keywords were added ...
DNA replication meets genetic exchange: Chromosomal damage and its repair by homologous recombination. Andrei Kuzminov ... DNA replication meets genetic exchange: Chromosomal damage and its repair by homologous recombination ... DNA replication meets genetic exchange: Chromosomal damage and its repair by homologous recombination ... DNA replication meets genetic exchange: Chromosomal damage and its repair by homologous recombination ...
Genetic recombination and complementation between bacteriophage T7 and cloned fragments of T7 DNA. J L Campbell, C C Richardson ... Genetic recombination and complementation between bacteriophage T7 and cloned fragments of T7 DNA ... Genetic recombination and complementation between bacteriophage T7 and cloned fragments of T7 DNA ... Genetic recombination and complementation between bacteriophage T7 and cloned fragments of T7 DNA ...
The problem with this idea is the fact that genetic recombination is now being shown to be a highly regulated and controlled ... Genetic recombination is directed away from functional genomic elements in mice. Nature. 485 (7400): 642-645. ... This process of exchanging DNA segments across sister chromatids is called genetic or homologous recombination and does not ... Evolutionists have speculated for years that genetic recombination is one of the key mechanisms generating mutations and ...
Mismatch repair stabilizes the cellular genome by correcting DNA replication errors and by blocking recombination events ... Mismatch repair in replication fidelity, genetic recombination, and cancer biology Annu Rev Biochem. 1996;65:101-33. doi: ... Mismatch repair stabilizes the cellular genome by correcting DNA replication errors and by blocking recombination events ...
View source for Genetic recombination/Related Articles. ← Genetic recombination/Related Articles. Jump to: navigation, search ...
... the effect of genetic recombination on a species capacity of adaptation. ... There has been much discussion of the evolutionary role of genetic recombination: the exchange of parental genetic material ... But what exactly is the advantage of recombination? This work shows that genetic recombination facilitates adaptation and it ... Evolutionary advantage of genetic recombination in the genome measured for first time. Universitat Autonoma de Barcelona ...
During sexual reproduction, genes from both the mother and the father mix and mingle to produce a genetic combination unique to ... Scientists generate the most precise map of genetic recombination ever. July 10, 2008 Genetic recombination, the process by ... The importance of genetic recombination. "Natural selection works best when theres a diversity of genotypes to act upon," says ... Scientists discover gene controlling genetic recombination rates. April 20, 2018, University of Rochester ...
481: Genetic Toxicology: Saacharomyces cerevisiae, Miotic Recombination Assay Following the OECD Council decision, the Test ... Guideline 481 Genetic Toxicology: Saacharomyces cerevisiae, Miotic Recombination Assay was deleted on 2nd April 2014. ...
Meiosis and sexual reproduction, however, result in a reassortment of the genetic material. Thi ... This reassortment, called genetic recombination, originates from three events during the reproductive cycle: ... In many cases, however, this event may be affected by the genetic composition of a gamete. For example, some sperm may be ... Crossing over. During prophase I, nonsister chromatids of homologous chromosomes exchange pieces of genetic material. As a ...
... falciparum genome has a high recombination rate, although it also follows the overall rule of meiosis in eukaryotes with an ... We detected 638 recombination events and constructed a high-resolution genetic map. Comparing genetic and physical maps, we ... we used a high-density tiling array to estimate the genetic recombination rate among 32 progeny of a P. falciparum genetic ... High recombination rates and hotspots in a Plasmodium falciparum genetic cross Genome Biol. 2011;12(4):R33. doi: 10.1186/gb- ...
Molecular population genetic analysis of a Streptococcus pyogenes bacteriophage-encoded hyaluronidase gene: recombination ...
... the process by which sexually reproducing organisms shuffle their genetic material when producing germ cells, leads to ... offspring with a new genetic make-up and influences the course of evolution. ... Scientists generate the most precise map of genetic recombination ever. July 10, 2008, Genetic recombination, the process by ... Scientists generate the most precise map of genetic recombination ever. July 10, 2008 Genetic recombination, the process by ...
  • Scientists in Rochester have discovered a gene in fruit flies that is responsible for the evolution of these recombination rates. (rochester.edu)
  • By studying two species of fruit flies, they discovered a gene, MEI-218, that controls the rate of recombination. (rochester.edu)
  • This is the first gene I know of that anyone has shown to be responsible for the evolution of recombination rates," Presgraves says. (rochester.edu)
  • In the regions of much lower DNA similarity, which occur as differences in gene order, gene content, and other major DNA sequence differences-the recombination rates were much lower. (icr.org)
  • Molecular population genetic analysis of a Streptococcus pyogenes bacteriophage-encoded hyaluronidase gene: recombination contributes to allelic va. (nih.gov)
  • In a different type of recombination, called non-crossover, a small piece of DNA is copied from one chromosome onto the other without reciprocal exchange leading to gene conversion. (phys.org)
  • We identified by linkage disequilibrium and recombination analyses only limited genetic recombination, which occurred exclusively within the 60-kDa glycoprotein gene subtype IbA10G2, a predominant subtype for outbreaks in industrialized nations and a virulent subtype in the study community. (cdc.gov)
  • The aim of the study was to determine genetic linkage between gene pairs, Co-4 2 / Phg-2 , on bean-chromosome Pv08 and Co-5 /"P.ult" on-chromosome Pv07, to increase the efficiency of dual selection of resistance genes for major bean diseases, with molecular markers. (academicjournals.org)
  • Recombination fraction r, among gene pairs, the likelihood of linkage, L(r), and logarithm of odds (LOD) scores were computed using the statistical relationship of likelihood which assumes a binomial distribution. (academicjournals.org)
  • In a recent reanalysis of the hemagglutinin (HA) gene of the 1918 strain it was proposed that recombination had occurred such that the majority of its globular domain (HA1) was acquired from a swine-lineage virus. (ed.ac.uk)
  • We assert that this is incorrect and that the apparent recombination in the 1918 HA gene is actually the result of a difference in the rate of evolution between HA1 and the HA2 stalk region among human influenza A viruses of the H1N1 subtype. (ed.ac.uk)
  • nThis animation describes how cloning occurs and how gene is inserted inside a plasmid during recombination process. (dnatube.com)
  • Here we show that in two mutant cell lines (XR-V15B and XR-V9B) from group 5, the genetic defects are in the gene encoding the 86-kDa subunit of the Ku autoantigen, a nuclear protein that binds to the double-stranded DNA ends. (asm.org)
  • Thus, Ku is an essential component of the pathway(s) utilized for the resolution of DNA double-strand breaks induced by either X rays or V(D)J recombination, and mutations in the Ku86 gene are responsible for the phenotype of group 5 cells. (asm.org)
  • This study offers broader implications on what gene clusters (including those involved with metabolism or supplementary metabolite creation) are constructed and taken care of and explains how recombination can be distorted in sex-determining areas in eukaryotes. (bioinf.org)
  • At Waseda University, education and training is mandatory in order to secure the safety of individuals engaged in gene recombination experiments and to prevent diffusion to the surrounding environment. (waseda.jp)
  • Individuals engaged in a gene recombination experiment must always attend the "Lecture on Gene Recombination Experiments" on Course [email protected] before beginning the experiment. (waseda.jp)
  • Teaching and administrative staff and students who are scheduled to newly begin gene recombination experiments at our school as research activities(Please attend this lecture separately from the advance lecture in experiment subjects. (waseda.jp)
  • It uses a full-likelihood method to infer the posterior distribution of recombination rates along the sequence under a variable recombination rate model assuming that the ratio of gene- conversion to crossing-over rate ( f ) is uniform along the sequence. (blogspot.com)
  • Although it is a classical genetics topic, genetic linkage remains an important concept to understand in order to grasp modern genetics research approaches including Single Nucleotide Polymorphism (SNP) mapping, Genome Wide Association Studies (GWAS), and gene discovery. (coursesource.org)
  • The toolbox for genetic research is expanding rapidly, and this overview presents a suite of tools generally referred to as reverse genetics that can be used to investigate gene function. (apsnet.org)
  • The process of disruption or alteration can either be targeted specifically as in the case of gene silencing or homologous recombination or can rely on non-targeted random disruptions (e.g., chemical mutagenesis, transposon mediated mutagenesis) followed by screening a library of individuals for lesions at a specific location. (apsnet.org)
  • A subsequent generation of genetic engineering techniques that emerged in the early 21st century centred on gene editing . (britannica.com)
  • Gene editing, based on a technology known as CRISPR-Cas9, allows researchers to customize a living organism's genetic sequence by making very specific changes to its DNA. (britannica.com)
  • Gene editing has a wide array of applications, being used for the genetic modification of crop plants and livestock and of laboratory model organisms (e.g., mice). (britannica.com)
  • The correction of genetic errors associated with disease in animals suggests that gene editing has potential applications in gene therapy for humans. (britannica.com)
  • Genetic engineering has advanced the understanding of many theoretical and practical aspects of gene function and organization. (britannica.com)
  • Modulation of homologous recombination repair gene polymorphisms on genetic damage in chromate exposed workers. (cdc.gov)
  • The gene polymorphisms in homologous recombination repair pathway could modulate chromate-induced genetic damage. (cdc.gov)
  • Finally, our multiple-breed GWAS found that SNPs in eight loci affected recombination rate and that the PRDM9 gene associated with hotspot usage in multiple cattle breeds, indicating a shared genetic basis for recombination across dairy cattle breeds. (beds.ac.uk)
  • It is thought that perhaps recombination occurred in chimpanzees dually infected with SIV that infects red-capped mangabeys and SIV that infects greater spot-nosed monkeys to generate a novel chimeric virus, SIVcpz. (asm.org)
  • 1 Evolutionists commonly try to buttress their claim of a universal tree of life by pointing to the genetic similarity between chimpanzees and humans. (icr.org)
  • Recombination varies greatly among species, as illustrated by the poor conservation of the recombination landscape between humans and chimpanzees. (blogspot.com)
  • Two independent pathways: a Blm-specific pathway and a RecqlS-specific pathway, respectively, are responsible for the restoration of stalled forks via non-recombination-based mechanism to suppress mitotic crossover and reduce cancer risk. (grantome.com)
  • 1 The researchers found that genetic recombination levels were much higher in regions of the genome between humans and chimps where sequence identity was higher. (icr.org)
  • We conducted a comparative population genetic analysis of virulent C. homini s subtype IbA10G2 in children living in a periurban community in Lima, Peru, by multilocus sequence typing (MLST) of 32 genetic markers. (cdc.gov)
  • First, recombination would help explain the appreciable differences in genetic sequence among various isolates of PRRSV. (aasv.org)
  • 1 Of course, mutation must also be involved to a considerable extent, because without prior mutational changes, ie, if all existing PRRSV had an identical sequence, recombination might be a moot point. (aasv.org)
  • A 3347-locus genetic recombination map of sequence-tagged sites reveals features of genome organization, transmission and evolution of cotton (Gossypium). (semanticscholar.org)
  • Complete nucleotide sequence and host range of South African cassava mosaic virus: further evidence for recombination amongst begomoviruses. (microbiologyresearch.org)
  • The concatenated sequence was screened for evidence of recombination using a variety of statistical methods, with each proposed event evaluated by comparing maximum-likelihood phylogenies of the recombinant section with the non-recombinant portion of the dataset. (uct.ac.za)
  • This week, the MalariaGEN P. falciparum genetic crosses project released a new data resource , comprising whole-genome sequence and genetic variation data from the parents and offspring of three parasite crosses. (malariagen.net)
  • Although modern DNA sequencing technology has transformed the study of genetic variation in malaria parasites, analysing the raw sequence data is a complex process with many sources of error. (malariagen.net)
  • Because the crosses give us this guidance on which data to trust, we've been able to gain new insights about different types of genetic variation, including insertions and deletions, complex sequence changes, and copy number variation," says Miles. (malariagen.net)
  • Recombination sites are typically between 30 and 200 nucleotides in length and consist of two motifs with a partial inverted-repeat symmetry, to which the recombinase binds, and which flank a central crossover sequence at which the recombination takes place. (wikipedia.org)
  • One implication of these findings is that at any one moment there will be linked genetic variants, exposed simultaneously to selection in the genome, and therefore selection will be sub-optimal due to the linkage cost. (eurekalert.org)
  • If linkage cost exists, wherever recombination is low there will be a greater density of selective variants that do not segregate freely, lowering the efficiency of the selection and therefore the adaptation rate. (eurekalert.org)
  • The results showed a very positive correlation between recombination and adaptation, corroborating the existence of the linkage cost in the genome. (eurekalert.org)
  • We designed a lesson that provides a practical and experimental context to target these common student difficulties in learning about linkage and recombination. (coursesource.org)
  • This lesson includes very interactive class sessions and a follow-up problem set and post-test that allows students to develop a deeper understanding of genetic linkage, and provides instructors with insights about student thinking. (coursesource.org)
  • Recombination is important-it's not hard to convince anyone of that-but when we look across different species, we see that the rates of crossing over are different," Brand says. (rochester.edu)
  • The team focused on two closely related species of fruit flies-Drosophila melanogaster and its sister species, Drosophila mauritiana-because large differences have evolved in their rates of recombination: D. mauritiana does about 1.5 times more crossing over than D. melanogaster. (phys.org)
  • Since most archaeal species are extremophilic and difficult to cultivate, current knowledge of recombination in the Archaea is confined largely to comparative genomics and biochemistry. (portlandpress.com)
  • Moreover, they give insight into recombination landscapes and between- species karyotype evolution. (wur.nl)
  • The results reinforce the assertion that infection of non-cultivated plant species leads to higher levels of standing genetic variability, and indicate that recombination, not adaptive selection, explains the higher begomovirus variability in non-cultivated hosts. (microbiologyresearch.org)
  • We examined a data set comprising 18 distinct strains from 13 named species for evidence of recombination. (uct.ac.za)
  • Comparative studies have shown wide variation in recombination rate among species, but the characterization of recombination features between cattle breeds has not yet been performed. (beds.ac.uk)
  • Collectively, our results generated breed- and sex-specific recombination maps for multiple cattle breeds, provided a comprehensive characterization and comparison of recombination patterns between breeds, and expanded our understanding of the breed-level variations in recombination features within an important livestock species. (beds.ac.uk)
  • Sex-specific recombination maps have been generated in several mammalian species with the sex difference in recombination confirmed. (beds.ac.uk)
  • The fundamental principles of recombination are likely to be shared between yeast and humans. (phys.org)
  • by Wendy Gibson, Lori Peacock, Vanessa Ferris, Katrin Fischer, Jennifer Livingstone, James Thomas, Mick Bailey Genetic recombination between pathogens derived from humans and livestock has the potential to create novel pathogen strains, highlighted by the influenza pandemic H1N1/09, which was derived from a re-assortment of swine, avian and human influenza A viruses. (medworm.com)
  • Here we investigated whether genetic recombination between subspecies of the protozoan parasite, Trypanosoma brucei, from humans and animals can generate new strains of human pathogen, T. b. rhodesiense (Tbr) responsible for sleeping sickness (Human African Trypanosomiasis, HAT) in East Africa. (medworm.com)
  • Scientists have long recognized that the exchange of genetic material by crossing over-known as recombination-is vital to natural selection. (rochester.edu)
  • They found an unexpectedly high degree of sharing and exchange of genetic material between the tiny, green, photosynthetic cyanobacteria Synechococcus , which are abundant in these scalding, inhospitable environments. (carnegiescience.edu)
  • We confirmed that male recombination map is 10% longer than the female map in all three cattle breeds, consistent with previously reported results in Holstein cattle. (beds.ac.uk)
  • This open access resource provides a foundation for further research into how genetic variation and sexual recombination affects parasite biology, at a much higher resolution than previously possible. (malariagen.net)
  • The first cross proved that parasites undergo sexual recombination whilst inside the mosquito . (malariagen.net)
  • This sexual recombination is central to how parasites evolve and adapt to new pressures such as antimalarial drugs, and the new P. falciparum crosses data resource provides a unique opportunity to study parasite recombination in detail. (malariagen.net)
  • We observed several different recombination patterns, including those that had crossovers only in gfp . (asm.org)
  • Genetic recombination is the production of offspring with combinations of traits that differ from those found in either parent. (wikipedia.org)
  • 3,4 Unless something goes wrong with the process, recombination typically allows for variations in non-vital traits while protecting core-cellular processes. (icr.org)
  • But few work has been done to study the genetic architecture of nutritional traits of the oyster. (springer.com)
  • Using this high-qualified genetic map, we then conducted QTL analysis for growth and nutritional traits, the latter of which includes glycogen, amino acid (AA), and fatty acid (FA). (springer.com)
  • Strong genetic correlations were evident among the recombinants, such that 22 measured traits could be well represented by only seven underlying factors, which accounted for 80% of the total variation. (wiley.com)