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).
Highly repetitive DNA sequences found in HETEROCHROMATIN, mainly near centromeres. They are composed of simple sequences (very short) (see MINISATELLITE REPEATS) repeated in tandem many times to form large blocks of sequence. Additionally, following the accumulation of mutations, these blocks of repeats have been repeated in tandem themselves. The degree of repetition is on the order of 1000 to 10 million at each locus. Loci are few, usually one or two per chromosome. They were called satellites since in density gradients, they often sediment as distinct, satellite bands separate from the bulk of genomic DNA owing to a distinct BASE COMPOSITION.
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).
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.
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.
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.
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 Analysis, DNA
A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.
The genetic complement of an organism, including all of its GENES, as represented in its DNA, or in some cases, its RNA.
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).
Tandem Repeat Sequences
Copies of DNA sequences which lie adjacent to each other in the same orientation (direct tandem repeats) or in the opposite direction to each other (INVERTED TANDEM REPEATS).
Specific regions that are mapped within a GENOME. Genetic loci are usually identified with a shorthand notation that indicates the chromosome number and the position of a specific band along the P or Q arm of the chromosome where they are found. For example the locus 6p21 is found within band 21 of the P-arm of CHROMOSOME 6. Many well known genetic loci are also known by common names that are associated with a genetic function or HEREDITARY DISEASE.
Loss of Heterozygosity
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.
Tandem arrays of moderately repetitive, short (10-60 bases) DNA sequences which are found dispersed throughout the GENOME, at the ends of chromosomes (TELOMERES), and clustered near telomeres. Their degree of repetition is two to several hundred at each locus. Loci number in the thousands but each locus shows a distinctive repeat unit.
The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.
Trinucleotide Repeat Expansion
An increased number of contiguous trinucleotide repeats in the DNA sequence from one generation to the next. The presence of these regions is associated with diseases such as FRAGILE X SYNDROME and MYOTONIC DYSTROPHY. Some CHROMOSOME FRAGILE SITES are composed of sequences where trinucleotide repeat expansion occurs.
An individual having different alleles at one or more loci regarding a specific character.
MutS Homolog 2 Protein
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.
Base Pair Mismatch
The presence of an uncomplimentary base in double-stranded DNA caused by spontaneous deamination of cytosine or adenine, mismatching during homologous recombination, or errors in DNA replication. Multiple, sequential base pair mismatches lead to formation of heteroduplex DNA; (NUCLEIC ACID HETERODUPLEXES).
Protein motif that contains a 33-amino acid long sequence that often occurs in tandem arrays. This repeating sequence of 33-amino acids was discovered in ANKYRIN where it is involved in interaction with the anion exchanger (ANION EXCHANGE PROTEIN 1, ERYTHROCYTE). Ankyrin repeats cooperatively fold into domains that mediate molecular recognition via protein-protein interactions.
The proportion of one particular in the total of all ALLELES for one genetic locus in a breeding POPULATION.
DNA Mismatch Repair
A DNA repair pathway involved in correction of errors introduced during DNA replication when an incorrect base, which cannot form hydrogen bonds with the corresponding base in the parent strand, is incorporated into the daughter strand. Excinucleases recognize the BASE PAIR MISMATCH and cause a segment of polynucleotide chain to be excised from the daughter strand, thereby removing the mismatched base. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)
Repetitive Sequences, Amino Acid
Colorectal Neoplasms, Hereditary Nonpolyposis
A group of autosomal-dominant inherited diseases in which COLON CANCER arises in discrete adenomas. Unlike FAMILIAL POLYPOSIS COLI with hundreds of polyps, hereditary nonpolyposis colorectal neoplasms occur much later, in the fourth and fifth decades. HNPCC has been associated with germline mutations in mismatch repair (MMR) genes. It has been subdivided into Lynch syndrome I or site-specific colonic cancer, and LYNCH SYNDROME II which includes extracolonic cancer.
A type of mutation in which a number of NUCLEOTIDES deleted from or inserted into a protein coding sequence is not divisible by three, thereby causing an alteration in the READING FRAMES of the entire coding sequence downstream of the mutation. These mutations may be induced by certain types of MUTAGENS or may occur spontaneously.
DNA Sequence, Unstable
A region of DNA that is highly polymorphic and is prone to strand breaks, rearrangements or other MUTATIONS because of the nature of its sequence. These regions often harbor palindromic, or repetitive sequences (REPETITIVE SEQUENCES, NUCLEIC ACID). Variability in stability of the DNA sequence is seen at CHROMOSOME FRAGILE SITES.
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.
Inverted Repeat Sequences
Copies of nucleic acid sequence that are arranged in opposing orientation. They may lie adjacent to each other (tandem) or be separated by some sequence that is not part of the repeat (hyphenated). They may be true palindromic repeats, i.e. read the same backwards as forward, or complementary which reads as the base complement in the opposite orientation. Complementary inverted repeats have the potential to form hairpin loop or stem-loop structures which results in cruciform structures (such as CRUCIFORM DNA) when the complementary inverted repeats occur in double stranded regions.
DNA Repeat Expansion
An increase number of repeats of a genomic, tandemly repeated DNA sequence from one generation to the next.
Adaptor Proteins, Signal Transducing
A broad category of carrier proteins that play a role in SIGNAL TRANSDUCTION. They generally contain several modular domains, each of which having its own binding activity, and act by forming complexes with other intracellular-signaling molecules. Signal-transducing adaptor proteins lack enzyme activity, however their activity can be modulated by other signal-transducing enzymes
Chromosomes, Human, Pair 3
The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.
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.
The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.