The chromosomal constitution of cells, in which each type of CHROMOSOME is represented twice. Symbol: 2N or 2X.
The chromosomal constitution of cells which deviate from the normal by the addition or subtraction of CHROMOSOMES, chromosome pairs, or chromosome fragments. In a normally diploid cell (DIPLOIDY) the loss of a chromosome pair is termed nullisomy (symbol: 2N-2), the loss of a single chromosome is MONOSOMY (symbol: 2N-1), the addition of a chromosome pair is tetrasomy (symbol: 2N+2), the addition of a single chromosome is TRISOMY (symbol: 2N+1).
The chromosomal constitution of cells, in which each type of CHROMOSOME is represented once. Symbol: N.
The degree of replication of the chromosome set in the karyotype.
The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained.
Mature male germ cells derived from SPERMATIDS. As spermatids move toward the lumen of the SEMINIFEROUS TUBULES, they undergo extensive structural changes including the loss of cytoplasm, condensation of CHROMATIN into the SPERM HEAD, formation of the ACROSOME cap, the SPERM MIDPIECE and the SPERM TAIL that provides motility.
A type of IN SITU HYBRIDIZATION in which target sequences are stained with fluorescent dye so their location and size can be determined using fluorescence microscopy. This staining is sufficiently distinct that the hybridization signal can be seen both in metaphase spreads and in interphase nuclei.
A condition of suboptimal concentration of SPERMATOZOA in the ejaculated SEMEN to ensure successful FERTILIZATION of an OVUM. In humans, oligospermia is defined as a sperm count below 20 million per milliliter semen.
A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.
Abnormal number or structure of chromosomes. Chromosome aberrations may result in CHROMOSOME DISORDERS.
The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.
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.
The chromosomal constitution of a cell containing multiples of the normal number of CHROMOSOMES; includes triploidy (symbol: 3N), tetraploidy (symbol: 4N), etc.
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.
A unisexual reproduction without the fusion of a male and a female gamete (FERTILIZATION). In parthenogenesis, an individual is formed from an unfertilized OVUM that did not complete MEIOSIS. Parthenogenesis occurs in nature and can be artificially induced.
A specific pair of human chromosomes in group A (CHROMOSOMES, HUMAN, 1-3) of the human chromosome classification.
Mapping of the KARYOTYPE of a cell.
The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.
Species- or subspecies-specific DNA (including COMPLEMENTARY DNA; conserved genes, whole chromosomes, or whole genomes) used in hybridization studies in order to identify microorganisms, to measure DNA-DNA homologies, to group subspecies, etc. The DNA probe hybridizes with a specific mRNA, if present. Conventional techniques used for testing for the hybridization product include dot blot assays, Southern blot assays, and DNA:RNA hybrid-specific antibody tests. Conventional labels for the DNA probe include the radioisotope labels 32P and 125I and the chemical label biotin. The use of DNA probes provides a specific, sensitive, rapid, and inexpensive replacement for cell culture techniques for diagnosing infections.
An assisted fertilization technique consisting of the microinjection of a single viable sperm into an extracted ovum. It is used principally to overcome low sperm count, low sperm motility, inability of sperm to penetrate the egg, or other conditions related to male infertility (INFERTILITY, MALE).
DNA present in neoplastic tissue.
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.
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.
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.
Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.
Reproduction without fusion of two types of cells, mostly found in ALGAE; FUNGI; and PLANTS. Asexual reproduction occurs in several ways, such as budding, fission, or splitting from "parent" cells. Only few groups of ANIMALS reproduce asexually or unisexually (PARTHENOGENESIS).
The total process by which organisms produce offspring. (Stedman, 25th ed)
Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)
Sexual activities of animals.
Sexual union of a male and a female in non-human species.

Mapping of the homothallic genes, HM alpha and HMa, in Saccharomyces yeasts. (1/1809)

Two of the three homothallic genes, HM alpha and HMa, showed direct linkage to the mating-type locus at approximately 73 and 98 strans (57 and 65 centimorgans [cM], respectively, whereas, the other, HO, showed no linkage to 25 standard markers distributed over 17 chromosomes including the mating-type locus. To determine whether the HM alpha and HMa loci located on the left or right side of the mating-type locus, equations for three factor analysis of three linked genes were derived. Tetrad data were collected and were compared with expected values by chi 2 statistics. Calculations indicated that the HM alpha gene is probably located on the right arm at 95 strans (65 cM) from the centromere and the HMa locus at approximately 90 strans (64 cM) on the left arm of chromosome III.  (+info)

C-myc overexpression and p53 loss cooperate to promote genomic instability. (2/1809)

p53 monitors genomic integrity at the G1 and G2/M cell cycle checkpoints. Cells lacking p53 may show gene amplification as well as the polyploidy or aneuploidy typical of many tumors. The pathways through which this develops, however, are not well defined. We demonstrate here that the combination of p53 inactivation and c-myc overexpression in diploid cells markedly accelerates the spontaneous development of tetraploidy. This is not seen with either N-myc or L-myc. Tetraploidy is accompanied by significantly higher levels of cyclin B and its associated cdc2 kinase activity. Mitotic spindle poisons accelerate the appearance of tetraploidy in cells either lacking functional p53 or overexpressing c-myc whereas the combination is additive. Restoration of p53 function in cells overexpressing c-myc causing rapid apoptosis, indicating that cells yet to become tetraploid have nonetheless suffered irreversible genomic and/or mitotic spindle damage. In the face of normal p53 function, such damage would either be repaired or trigger apoptotis. We propose that loss of p53 and overexpression of c-myc permits the emergence and survival of cells with increasingly severe damage and the eventual development of tetraploidy.  (+info)

The 3'-->5' exonucleases of DNA polymerases delta and epsilon and the 5'-->3' exonuclease Exo1 have major roles in postreplication mutation avoidance in Saccharomyces cerevisiae. (3/1809)

Replication fidelity is controlled by DNA polymerase proofreading and postreplication mismatch repair. We have genetically characterized the roles of the 5'-->3' Exo1 and the 3'-->5' DNA polymerase exonucleases in mismatch repair in the yeast Saccharomyces cerevisiae by using various genetic backgrounds and highly sensitive mutation detection systems that are based on long and short homonucleotide runs. Genetic interactions were examined among DNA polymerase epsilon (pol2-4) and delta (pol3-01) mutants defective in 3'-->5' proofreading exonuclease, mutants defective in the 5'-->3' exonuclease Exo1, and mismatch repair mutants (msh2, msh3, or msh6). These three exonucleases play an important role in mutation avoidance. Surprisingly, the mutation rate in an exo1 pol3-01 mutant was comparable to that in an msh2 pol3-01 mutant, suggesting that they participate directly in postreplication mismatch repair as well as in other DNA metabolic processes.  (+info)

Perturbation of mammalian cell division. III. The topography and kinetics of extrusion subdivision. (4/1809)

If mitotic-arrested, cold-stored HeLa cells are incubated at 37 degrees C a proportion of the population divides by an aberrant process which we have called subdivision by extrusion. This process has been studied by time-lapse photography and shown to differ from normal cleavage in several respects. The cell surface becomes more generally mobile and, instead of producing the precisely localized furrowing activity of cytokinesis, gives rise to multiple surface protrusions. These protrusions enlarge at the expense of the parent cell and develop into a cluster of small daughter cells (mini segregants). The surface structure of the cell, as seen by scanning electron microscopy, also changes; the microvilli characteristic of interphase, metaphase and cleaving HeLa cells are lost during extrusion and the cell surface becomes smooth. Extrusion activity is much more variable than division by cleavage in terms of both topography and kinetics, and in general takes longer to complete. Some cells in the cold-treated populations divide by mixtures of cleavage and extrusion or by cleavage alone. The relative numbers of cells dividing in different ways vary with the conditions of pretreatment and incubation of the mitotic cells. The greater the perturbation (e.g. longer cold storage), the greater the proportion of extruding rather than cleaving cells. Human diploid cells can also be induced to subdivide by extrusion. Possible mechanisms underlying the different types of division activity are discussed.  (+info)

TNF-alpha increases ceramide without inducing apoptosis in alveolar type II epithelial cells. (5/1809)

Ceramide is a bioactive lipid mediator that has been observed to induce apoptosis in vitro. The purpose of this study was to determine whether endogenous ceramide, generated in response to in vivo administration of tumor necrosis factor-alpha (TNF-alpha), increases apoptosis in primary rat alveolar type II epithelial cells. Intratracheal instillation of TNF-alpha (5 microgram) produced a decrease in sphingomyelin and activation of a neutral sphingomyelinase. These changes were associated with a significant increase in lung ceramide content. TNF-alpha concomitantly activated the p42/44 extracellular signal-related kinases and induced nuclear factor-kappaB activation in the lung. Hypodiploid nuclei studies revealed that intratracheal TNF-alpha did not increase type II cell apoptosis compared with that in control cells after isolation. A novel observation from separate in vitro studies demonstrated that type II cells undergo a gradual increase in apoptosis after time in culture, a process that was accelerated by exposure of cells to ultraviolet light. However, culture of cells with a cell-permeable ceramide, TNF-alpha, or a related ligand, anti-CD95, did not increase apoptosis above the control level. The results suggest that ceramide resulting from TNF-alpha activation of sphingomyelin hydrolysis might activate the mitogen-activated protein kinase and nuclear factor-kappaB pathways without increasing programmed cell death in type II cells.  (+info)

Progression from colorectal adenoma to carcinoma is associated with non-random chromosomal gains as detected by comparative genomic hybridisation. (6/1809)

AIMS: Chromosomal gains and losses were surveyed by comparative genomic hybridisation (CGH) in a series of colorectal adenomas and carcinomas, in search of high risk genomic changes involved in colorectal carcinogenesis. METHODS: Nine colorectal adenomas and 14 carcinomas were analysed by CGH, and DNA ploidy was assessed with both flow and image cytometry. RESULTS: In the nine adenomas analysed, an average of 6.6 (range 1 to 11) chromosomal aberrations were identified. In the 14 carcinomas an average of 11.9 (range 5 to 17) events were found per tumour. In the adenomas the number of gains and losses was in balance (3.6 v 3.0) while in carcinomas gains occurred more often than losses (8.2 v 3.7). Frequent gains involved 13q, 7p, 8q, and 20q, whereas losses most often occurred at 18q, 4q, and 8p. Gains of 13q, 8q, and 20q, and loss of 18q occurred more often in carcinomas than in adenomas (p = 0.005, p = 0.05, p = 0.05, and p = 0.02, respectively). Aneuploid tumours showed more gains than losses (mean 9.3 v 4.9, p = 0.02), in contrast to diploid tumours where gains and losses were nearly balanced (mean 3.1 v 4.1, p = 0.5). CONCLUSIONS: The most striking difference between chromosomal aberrations in colorectal adenomas and carcinomas, as detected by CGH, is an increased number of chromosomal gains that show a nonrandom distribution. Gains of 13q and also of 20q and 8q seem especially to be involved in the progression of adenomas to carcinomas, possibly owing to low level overexpression of oncogenes at these loci.  (+info)

Mutator phenotypes conferred by MLH1 overexpression and by heterozygosity for mlh1 mutations. (7/1809)

Loss of DNA mismatch repair due to mutation or diminished expression of the MLH1 gene is associated with genome instability and cancer. In this study, we used a yeast model system to examine three circumstances relevant to modulation of MLH1 function. First, overexpression of wild-type MLH1 was found to cause a strong elevation of mutation rates at three different loci, similar to the mutator effect of MLH1 gene inactivation. Second, haploid yeast strains with any of six mlh1 missense mutations that mimic germ line mutations found in human cancer patients displayed a strong mutator phenotype consistent with loss of mismatch repair function. Five of these mutations affect amino acids that are homologous to residues suggested by recent crystal structure and biochemical analysis of Escherichia coli MutL to participate in ATP binding and hydrolysis. Finally, using a highly sensitive reporter gene, we detected a mutator phenotype of diploid yeast strains that are heterozygous for mlh1 mutations. Evidence suggesting that this mutator effect results not from reduced mismatch repair in the MLH1/mlh1 cells but rather from loss of the wild-type MLH1 allele in a fraction of cells is presented. Exposure to bleomycin or to UV irradiation strongly enhanced mutagenesis in the heterozygous strain but had little effect on the mutation rate in the wild-type strain. This damage-induced hypermutability may be relevant to cancer in humans with germ line mutations in only one MLH1 allele.  (+info)

The organization of genetic diversity in the parthenogenetic lizard Cnemidophorus tesselatus. (8/1809)

The parthogenetic lizard species Cnemidophorus tesselatus is composed of diploid populations formed by hybridization of the bisexual species C. tigris and C. septemvittatus, and of triploid populations derived from a cross between diploid tesselatus and a third bisexual species, C. sexlineatus. An analysis of allozymic variation in proteins encoded by 21 loci revealed that, primarily because of hybrid origin, individual heterozygosity in tesselatus is much higher (0.560 in diploids and 0.714 in triploids) than in the parental bisexual species (mean, 0.059). All triploid individuals apparently represent a single clone, but 12 diploid clones were identified on the basis of genotypic diversity occurring at six loci. From one to four clones were recorded in each population sampled. Three possible sources of clonal diversity in the diploid parthenogens were identified: mutation at three loci has produced three clones, each confined to a single locality; genotypic diversity at two loci apparently caused by multiple hybridization of the bisexual species accounts for four clones; and the remaining five clones apparently have arisen through recombination at three loci. The relatively limited clonal diversity of tesselatus suggests a recent origin. The evolutionary potential of tesselatus and of parthenogenetic forms in general may be less severely limited than has generally been supposed.  (+info)

Diploidy is a term used in genetics to describe the state of having two sets of chromosomes in each cell. In diploid organisms, one set of chromosomes is inherited from each parent, resulting in a total of 2 sets of chromosomes.

In humans, for example, most cells are diploid and contain 46 chromosomes arranged in 23 pairs. This includes 22 pairs of autosomal chromosomes and one pair of sex chromosomes (XX in females or XY in males). Diploidy is a characteristic feature of many complex organisms, including animals, plants, and fungi.

Diploid cells can undergo a process called meiosis, which results in the formation of haploid cells that contain only one set of chromosomes. These haploid cells can then combine with other haploid cells during fertilization to form a new diploid organism.

Abnormalities in diploidy can lead to genetic disorders, such as Down syndrome, which occurs when an individual has three copies of chromosome 21 instead of the typical two. This extra copy of the chromosome can result in developmental delays and intellectual disabilities.

Aneuploidy is a medical term that refers to an abnormal number of chromosomes in a cell. Chromosomes are thread-like structures located inside the nucleus of cells that contain genetic information in the form of genes.

In humans, the normal number of chromosomes in a cell is 46, arranged in 23 pairs. Aneuploidy occurs when there is an extra or missing chromosome in one or more of these pairs. For example, Down syndrome is a condition that results from an extra copy of chromosome 21, also known as trisomy 21.

Aneuploidy can arise during the formation of gametes (sperm or egg cells) due to errors in the process of cell division called meiosis. These errors can result in eggs or sperm with an abnormal number of chromosomes, which can then lead to aneuploidy in the resulting embryo.

Aneuploidy is a significant cause of birth defects and miscarriages. The severity of the condition depends on which chromosomes are affected and the extent of the abnormality. In some cases, aneuploidy may have no noticeable effects, while in others it can lead to serious health problems or developmental delays.

Haploidy is a term used in genetics to describe the condition of having half the normal number of chromosomes in a cell or an organism. In humans, for example, a haploid cell contains 23 chromosomes, whereas a diploid cell has 46 chromosomes.

Haploid cells are typically produced through a process called meiosis, which is a type of cell division that occurs in the reproductive organs of sexually reproducing organisms. During meiosis, a diploid cell undergoes two rounds of division to produce four haploid cells, each containing only one set of chromosomes.

In humans, haploid cells are found in the sperm and egg cells, which fuse together during fertilization to create a diploid zygote with 46 chromosomes. Haploidy is important for maintaining the correct number of chromosomes in future generations and preventing genetic abnormalities that can result from having too many or too few chromosomes.

Ploidy is a term used in genetics to describe the number of sets of chromosomes in a cell or an organism. The ploidy level can have important implications for genetic inheritance and expression, as well as for evolutionary processes such as speciation and hybridization.

In most animals, including humans, the normal ploidy level is diploid, meaning that each cell contains two sets of chromosomes - one set inherited from each parent. However, there are also many examples of polyploidy, in which an organism has more than two sets of chromosomes.

Polyploidy can arise through various mechanisms, such as genome duplication or hybridization between different species. In some cases, polyploidy may confer evolutionary advantages, such as increased genetic diversity and adaptability to new environments. However, it can also lead to reproductive isolation and the formation of new species.

In plants, polyploidy is relatively common and has played a significant role in their evolution and diversification. Many crop plants are polyploids, including wheat, cotton, and tobacco. In some cases, artificial induction of polyploidy has been used to create new varieties with desirable traits for agriculture and horticulture.

Overall, ploidy is an important concept in genetics and evolution, with implications for a wide range of biological processes and phenomena.

The Y chromosome is one of the two sex-determining chromosomes in humans and many other animals, along with the X chromosome. The Y chromosome contains the genetic information that helps to determine an individual's sex as male. It is significantly smaller than the X chromosome and contains fewer genes.

The Y chromosome is present in males, who inherit it from their father. Females, on the other hand, have two X chromosomes, one inherited from each parent. The Y chromosome includes a gene called SRY (sex-determining region Y), which initiates the development of male sexual characteristics during embryonic development.

It is worth noting that the Y chromosome has a relatively high rate of genetic mutation and degeneration compared to other chromosomes, leading to concerns about its long-term viability in human evolution. However, current evidence suggests that the Y chromosome has been stable for at least the past 25 million years.

Spermatozoa are the male reproductive cells, or gametes, that are produced in the testes. They are microscopic, flagellated (tail-equipped) cells that are highly specialized for fertilization. A spermatozoon consists of a head, neck, and tail. The head contains the genetic material within the nucleus, covered by a cap-like structure called the acrosome which contains enzymes to help the sperm penetrate the female's egg (ovum). The long, thin tail propels the sperm forward through fluid, such as semen, enabling its journey towards the egg for fertilization.

In situ hybridization, fluorescence (FISH) is a type of molecular cytogenetic technique used to detect and localize the presence or absence of specific DNA sequences on chromosomes through the use of fluorescent probes. This technique allows for the direct visualization of genetic material at a cellular level, making it possible to identify chromosomal abnormalities such as deletions, duplications, translocations, and other rearrangements.

The process involves denaturing the DNA in the sample to separate the double-stranded molecules into single strands, then adding fluorescently labeled probes that are complementary to the target DNA sequence. The probe hybridizes to the complementary sequence in the sample, and the location of the probe is detected by fluorescence microscopy.

FISH has a wide range of applications in both clinical and research settings, including prenatal diagnosis, cancer diagnosis and monitoring, and the study of gene expression and regulation. It is a powerful tool for identifying genetic abnormalities and understanding their role in human disease.

Oligospermia is a medical term used to describe a condition in which the semen contains a lower than normal number of sperm. Generally, a sperm count of less than 15 million sperm per milliliter (ml) of semen is considered to be below the normal range.

Oligospermia can make it more difficult for a couple to conceive naturally and may require medical intervention such as intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). The condition can result from various factors, including hormonal imbalances, genetic abnormalities, varicocele, environmental factors, and certain medications.

It's important to note that oligospermia is not the same as azoospermia, which is a condition where there is no sperm present in the semen at all.

Human chromosome pair 18 consists of two rod-shaped structures present in the nucleus of each cell of the human body. Chromosomes are made up of DNA, protein, and RNA, and they carry genetic information that determines an individual's physical characteristics, biochemical processes, and susceptibility to disease.

Chromosome pair 18 is one of the 23 pairs of chromosomes that make up the human genome. Each member of chromosome pair 18 has a length of about 75 million base pairs and contains around 600 genes. Chromosome pair 18 is also known as the "smart chromosome" because it contains many genes involved in brain development, function, and cognition.

Abnormalities in chromosome pair 18 can lead to genetic disorders such as Edwards syndrome (trisomy 18), in which there is an extra copy of chromosome 18, or deletion of a portion of the chromosome, leading to various developmental and cognitive impairments.

Chromosome aberrations refer to structural and numerical changes in the chromosomes that can occur spontaneously or as a result of exposure to mutagenic agents. These changes can affect the genetic material encoded in the chromosomes, leading to various consequences such as developmental abnormalities, cancer, or infertility.

Structural aberrations include deletions, duplications, inversions, translocations, and rings, which result from breaks and rearrangements of chromosome segments. Numerical aberrations involve changes in the number of chromosomes, such as aneuploidy (extra or missing chromosomes) or polyploidy (multiples of a complete set of chromosomes).

Chromosome aberrations can be detected and analyzed using various cytogenetic techniques, including karyotyping, fluorescence in situ hybridization (FISH), and comparative genomic hybridization (CGH). These methods allow for the identification and characterization of chromosomal changes at the molecular level, providing valuable information for genetic counseling, diagnosis, and research.

Male infertility is a condition characterized by the inability to cause pregnancy in a fertile female. It is typically defined as the failure to achieve a pregnancy after 12 months or more of regular unprotected sexual intercourse.

The causes of male infertility can be varied and include issues with sperm production, such as low sperm count or poor sperm quality, problems with sperm delivery, such as obstructions in the reproductive tract, or hormonal imbalances that affect sperm production. Other factors that may contribute to male infertility include genetic disorders, environmental exposures, lifestyle choices, and certain medical conditions or treatments.

It is important to note that male infertility can often be treated or managed with medical interventions, such as medication, surgery, or assisted reproductive technologies (ART). A healthcare provider can help diagnose the underlying cause of male infertility and recommend appropriate treatment options.

The X chromosome is one of the two types of sex-determining chromosomes in humans (the other being the Y chromosome). It's one of the 23 pairs of chromosomes that make up a person's genetic material. Females typically have two copies of the X chromosome (XX), while males usually have one X and one Y chromosome (XY).

The X chromosome contains hundreds of genes that are responsible for the production of various proteins, many of which are essential for normal bodily functions. Some of the critical roles of the X chromosome include:

1. Sex Determination: The presence or absence of the Y chromosome determines whether an individual is male or female. If there is no Y chromosome, the individual will typically develop as a female.
2. Genetic Disorders: Since females have two copies of the X chromosome, they are less likely to be affected by X-linked genetic disorders than males. Males, having only one X chromosome, will express any recessive X-linked traits they inherit.
3. Dosage Compensation: To compensate for the difference in gene dosage between males and females, a process called X-inactivation occurs during female embryonic development. One of the two X chromosomes is randomly inactivated in each cell, resulting in a single functional copy per cell.

The X chromosome plays a crucial role in human genetics and development, contributing to various traits and characteristics, including sex determination and dosage compensation.

Polyploidy is a condition in which a cell or an organism has more than two sets of chromosomes, unlike the typical diploid state where there are only two sets (one from each parent). Polyploidy can occur through various mechanisms such as errors during cell division, fusion of egg and sperm cells that have an abnormal number of chromosomes, or through the reproduction process in plants.

Polyploidy is common in the plant kingdom, where it often leads to larger size, increased biomass, and sometimes hybrid vigor. However, in animals, polyploidy is less common and usually occurs in only certain types of cells or tissues, as most animals require a specific number of chromosomes for normal development and reproduction. In humans, polyploidy is typically not compatible with life and can lead to developmental abnormalities and miscarriage.

Meiosis is a type of cell division that results in the formation of four daughter cells, each with half the number of chromosomes as the parent cell. It is a key process in sexual reproduction, where it generates gametes or sex cells (sperm and eggs).

The process of meiosis involves one round of DNA replication followed by two successive nuclear divisions, meiosis I and meiosis II. In meiosis I, homologous chromosomes pair, form chiasma and exchange genetic material through crossing over, then separate from each other. In meiosis II, sister chromatids separate, leading to the formation of four haploid cells. This process ensures genetic diversity in offspring by shuffling and recombining genetic information during the formation of gametes.

Parthenogenesis is a form of asexual reproduction in which offspring develop from unfertilized eggs or ovums. It occurs naturally in some plant and insect species, as well as a few vertebrates such as reptiles and fish. Parthenogenesis does not involve the fusion of sperm and egg cells; instead, the development of offspring is initiated by some other trigger, such as a chemical or physical stimulus. This type of reproduction results in offspring that are genetically identical to the parent organism. In humans and other mammals, parthenogenesis is not a natural occurrence and would require scientific intervention to induce.

Human chromosome pair 1 refers to the first pair of chromosomes in a set of 23 pairs found in the cells of the human body, excluding sex cells (sperm and eggs). Each cell in the human body, except for the gametes, contains 46 chromosomes arranged in 23 pairs. These chromosomes are rod-shaped structures that contain genetic information in the form of DNA.

Chromosome pair 1 is the largest pair, making up about 8% of the total DNA in a cell. Each chromosome in the pair consists of two arms - a shorter p arm and a longer q arm - connected at a centromere. Chromosome 1 carries an estimated 2,000-2,500 genes, which are segments of DNA that contain instructions for making proteins or regulating gene expression.

Defects or mutations in the genes located on chromosome 1 can lead to various genetic disorders and diseases, such as Charcot-Marie-Tooth disease type 1A, Huntington's disease, and certain types of cancer.

Karyotyping is a medical laboratory test used to study the chromosomes in a cell. It involves obtaining a sample of cells from a patient, usually from blood or bone marrow, and then staining the chromosomes so they can be easily seen under a microscope. The chromosomes are then arranged in pairs based on their size, shape, and other features to create a karyotype. This visual representation allows for the identification and analysis of any chromosomal abnormalities, such as extra or missing chromosomes, or structural changes like translocations or inversions. These abnormalities can provide important information about genetic disorders, diseases, and developmental problems.

Biological evolution is the change in the genetic composition of populations of organisms over time, from one generation to the next. It is a process that results in descendants differing genetically from their ancestors. Biological evolution can be driven by several mechanisms, including natural selection, genetic drift, gene flow, and mutation. These processes can lead to changes in the frequency of alleles (variants of a gene) within populations, resulting in the development of new species and the extinction of others over long periods of time. Biological evolution provides a unifying explanation for the diversity of life on Earth and is supported by extensive evidence from many different fields of science, including genetics, paleontology, comparative anatomy, and biogeography.

A DNA probe is a single-stranded DNA molecule that contains a specific sequence of nucleotides, and is labeled with a detectable marker such as a radioisotope or a fluorescent dye. It is used in molecular biology to identify and locate a complementary sequence within a sample of DNA. The probe hybridizes (forms a stable double-stranded structure) with its complementary sequence through base pairing, allowing for the detection and analysis of the target DNA. This technique is widely used in various applications such as genetic testing, diagnosis of infectious diseases, and forensic science.

Intracytoplasmic Sperm Injection (ICSI) is a specialized form of assisted reproductive technology (ART), specifically used in the context of in vitro fertilization (IVF). It involves the direct injection of a single sperm into the cytoplasm of a mature egg (oocyte) to facilitate fertilization. This technique is often used when there are issues with male infertility, such as low sperm count or poor sperm motility, to increase the chances of successful fertilization. The resulting embryos can then be transferred to the uterus in hopes of achieving a pregnancy.

The term "DNA, neoplasm" is not a standard medical term or concept. DNA refers to deoxyribonucleic acid, which is the genetic material present in the cells of living organisms. A neoplasm, on the other hand, is a tumor or growth of abnormal tissue that can be benign (non-cancerous) or malignant (cancerous).

In some contexts, "DNA, neoplasm" may refer to genetic alterations found in cancer cells. These genetic changes can include mutations, amplifications, deletions, or rearrangements of DNA sequences that contribute to the development and progression of cancer. Identifying these genetic abnormalities can help doctors diagnose and treat certain types of cancer more effectively.

However, it's important to note that "DNA, neoplasm" is not a term that would typically be used in medical reports or research papers without further clarification. If you have any specific questions about DNA changes in cancer cells or neoplasms, I would recommend consulting with a healthcare professional or conducting further research on the topic.

Genetic recombination is the process by which genetic material is exchanged between two similar or identical molecules of DNA during meiosis, resulting in new combinations of genes on each chromosome. This exchange occurs during crossover, where segments of DNA are swapped between non-sister homologous chromatids, creating genetic diversity among the offspring. It is a crucial mechanism for generating genetic variability and facilitating evolutionary change within populations. Additionally, recombination also plays an essential role in DNA repair processes through mechanisms such as homologous recombinational repair (HRR) and non-homologous end joining (NHEJ).

Genetic models are theoretical frameworks used in genetics to describe and explain the inheritance patterns and genetic architecture of traits, diseases, or phenomena. These models are based on mathematical equations and statistical methods that incorporate information about gene frequencies, modes of inheritance, and the effects of environmental factors. They can be used to predict the probability of certain genetic outcomes, to understand the genetic basis of complex traits, and to inform medical management and treatment decisions.

There are several types of genetic models, including:

1. Mendelian models: These models describe the inheritance patterns of simple genetic traits that follow Mendel's laws of segregation and independent assortment. Examples include autosomal dominant, autosomal recessive, and X-linked inheritance.
2. Complex trait models: These models describe the inheritance patterns of complex traits that are influenced by multiple genes and environmental factors. Examples include heart disease, diabetes, and cancer.
3. Population genetics models: These models describe the distribution and frequency of genetic variants within populations over time. They can be used to study evolutionary processes, such as natural selection and genetic drift.
4. Quantitative genetics models: These models describe the relationship between genetic variation and phenotypic variation in continuous traits, such as height or IQ. They can be used to estimate heritability and to identify quantitative trait loci (QTLs) that contribute to trait variation.
5. Statistical genetics models: These models use statistical methods to analyze genetic data and infer the presence of genetic associations or linkage. They can be used to identify genetic risk factors for diseases or traits.

Overall, genetic models are essential tools in genetics research and medical genetics, as they allow researchers to make predictions about genetic outcomes, test hypotheses about the genetic basis of traits and diseases, and develop strategies for prevention, diagnosis, and treatment.

A mutation is a permanent change in the DNA sequence of an organism's genome. Mutations can occur spontaneously or be caused by environmental factors such as exposure to radiation, chemicals, or viruses. They may have various effects on the organism, ranging from benign to harmful, depending on where they occur and whether they alter the function of essential proteins. In some cases, mutations can increase an individual's susceptibility to certain diseases or disorders, while in others, they may confer a survival advantage. Mutations are the driving force behind evolution, as they introduce new genetic variability into populations, which can then be acted upon by natural selection.

Flow cytometry is a medical and research technique used to measure physical and chemical characteristics of cells or particles, one cell at a time, as they flow in a fluid stream through a beam of light. The properties measured include:

* Cell size (light scatter)
* Cell internal complexity (granularity, also light scatter)
* Presence or absence of specific proteins or other molecules on the cell surface or inside the cell (using fluorescent antibodies or other fluorescent probes)

The technique is widely used in cell counting, cell sorting, protein engineering, biomarker discovery and monitoring disease progression, particularly in hematology, immunology, and cancer research.

Asexual reproduction in a medical context refers to a type of reproduction that does not involve the fusion of gametes (sex cells) or the exchange of genetic material between two parents. In asexual reproduction, an organism creates offspring that are genetically identical to itself. This can occur through various mechanisms, such as budding, binary fission, fragmentation, or vegetative reproduction. Asexual reproduction is common in some plants, fungi, and unicellular organisms, but it also occurs in certain animals, such as starfish and some types of flatworms. This mode of reproduction allows for rapid population growth and can be advantageous in stable environments where genetic diversity is not essential for survival.

Reproduction, in the context of biology and medicine, refers to the process by which organisms produce offspring. It is a complex process that involves the creation, development, and growth of new individuals from parent organisms. In sexual reproduction, this process typically involves the combination of genetic material from two parents through the fusion of gametes (sex cells) such as sperm and egg cells. This results in the formation of a zygote, which then develops into a new individual with a unique genetic makeup.

In contrast, asexual reproduction does not involve the fusion of gametes and can occur through various mechanisms such as budding, fragmentation, or parthenogenesis. Asexual reproduction results in offspring that are genetically identical to the parent organism.

Reproduction is a fundamental process that ensures the survival and continuation of species over time. It is also an area of active research in fields such as reproductive medicine, where scientists and clinicians work to understand and address issues related to human fertility, contraception, and genetic disorders.

An encyclopedia is a comprehensive reference work containing articles on various topics, usually arranged in alphabetical order. In the context of medicine, a medical encyclopedia is a collection of articles that provide information about a wide range of medical topics, including diseases and conditions, treatments, tests, procedures, and anatomy and physiology. Medical encyclopedias may be published in print or electronic formats and are often used as a starting point for researching medical topics. They can provide reliable and accurate information on medical subjects, making them useful resources for healthcare professionals, students, and patients alike. Some well-known examples of medical encyclopedias include the Merck Manual and the Stedman's Medical Dictionary.

Sexual behavior in animals refers to a variety of behaviors related to reproduction and mating that occur between members of the same species. These behaviors can include courtship displays, mating rituals, and various physical acts. The specific forms of sexual behavior displayed by a given species are influenced by a combination of genetic, hormonal, and environmental factors.

In some animals, sexual behavior is closely tied to reproductive cycles and may only occur during certain times of the year or under specific conditions. In other species, sexual behavior may be more frequent and less closely tied to reproduction, serving instead as a means of social bonding or communication.

It's important to note that while humans are animals, the term "sexual behavior" is often used in a more specific sense to refer to sexual activities between human beings. The study of sexual behavior in animals is an important area of research within the field of animal behavior and can provide insights into the evolutionary origins of human sexual behavior as well as the underlying mechanisms that drive it.

Copulation is the act of sexual reproduction in animals, achieved through the process of mating and engaging in sexual intercourse. It involves the insertion of the male's reproductive organ (the penis) into the female's reproductive organ (vagina), followed by the ejaculation of semen, which contains sperm. The sperm then travels up through the cervix and into the uterus, where they may fertilize an egg or ovum that has been released from one of the ovaries.

In a broader sense, copulation can also refer to the act of reproduction in other organisms, such as plants, fungi, and protists, which may involve different processes such as pollination, fusion of gametes, or vegetative reproduction.

The advantage of diploidy, heterosis, only exists in the diploid life generation. Bryophytes retain sexual reproduction despite ... Otto, S.P.; Goldstein, D.B. (1992). "Recombination and the Evolution of Diploidy". Genetics. 131 (3): 745-751. doi:10.1093/ ...
Haploidy or diploidy: which is better? Nature 351:314-315 Kondrashov AS & Kondrashov FA. 1999. Interactions among quantitative ...
Gottlieb, Yuval; Zchori-Fein, Einat (4 September 2002). "Diploidy restoration in Wolbachia-infected Muscidifurax uniraptor ( ... where meiosis occurs in the developing oocyte and diploidy is restored by fusing the meiotic or mitotic products yielding ...
In Parthenolecanium, males are born from unfertilized eggs but diploidy is briefly restored by fusion of haploid cleave nuclei ... and based on how diploidy is restored in unfertilized eggs. The evolution of these systems are thought to be the result of ...
It has been shown that diploidy is restored by terminal fusion. After the first stage of meiosis, the pronucleus fuses with its ...
Haplo-diploidy, where one sex is diploid, and the other haploid. It is a common arrangement in the Hymenoptera, and in some ... A major exception to diploidy in humans is gametes (sperm and egg cells) which are haploid with 23 unpaired chromosomes, and ...
Kleiman, Maya; Tannenbaum, Emmanuel (2009). "Diploidy and the selective advantage for sexual reproduction in unicellular ...
The term ploidy is a back-formation from haploidy and diploidy. "Ploid" is a combination of Ancient Greek -πλόος (-plóos, "- ... Some studies suggest that selection is more likely to favor diploidy in host species and haploidy in parasite species. However ...
Other functions of the esg include Esg maintains diploidy in imaginal cells. Esg mutant flies showed polyploid abdominal ... Fuse, N; Hirose, S; Hayashi, S (1994-10-01). "Diploidy of Drosophila imaginal cells is maintained by a transcriptional ...
Usually, organisms have two sets of chromosomes, otherwise known as a diploidy. However, either naturally or through the use of ...
doi:10.1002/j.1537-2197.1982.tb13284.x. Jackson, R. C. (1982). "Polyploidy and Diploidy: New Perspectives on Chromosome Pairing ...
The higher rates of aneuploidy and diploidy in the sperm cells of those who have undergone vasectomy reversal may lead to a ... Sukcharoen, Nares; Ngeamvijawat, J; Sithipravej, T; Promviengchai, S (2003). "High sex chromosome aneuploidy and diploidy rate ...
This fertilization restores diploidy and results in expression of maternal and paternal traits in somatic tissue. These ...
Genome wide UPD, also called uniparental diploidy, is when all chromosomes are inherited from one parent. Only in mosaic form ...
Diploidy might be restored by the doubling of the chromosomes without cell division before meiosis begins or after meiosis is ... the ploidy is restored to diploidy by various means. This is because haploid individuals are not viable in most species. In ...
This disorder is called "numerical mosaicism". This mosaicism, especially of diploidy and polyploidy, can lead to the failure ...
For instance, the overall survival of patients with brain glioma reduced from 93 months (diploidy) to 24 months. In conclusion ...
Loss of diploidy (heterozygosity) and extensive breast inflammation upon first clinical examination are associated with a ...
Diploidy might be restored by the doubling of the chromosomes without cell division before meiosis begins or after meiosis is ...
... vulgare exhibiting diploidy. They have mostly similar distribution area in Europe, but L. vulgare is more common in North ...
In Hymenoptera (ants, bees and wasps), sex determination is by haplo-diploidy: the females are all diploid, the males are ...
Diploidy occurs through either the fusion of two haploid sperm cells or the duplication of chromosomes from one haploid sperm ...
Consider a gene with two alleles, A or B. In diploidy, populations consisting of N individuals have 2N copies of each gene. An ...
Yamazaki K, Yahata H, Kobayashi N, Makioka T. Egg maturation and parthenogenetic recovery of diploidy in the scorpion Liocheles ...
... diploidy). These duplicated genes may pose a problem for the de novo assembly of sequence fragments, because repeat sequences ...
... by maintaining diploidy or polyploidy. Genome redundancy would allow a damaged RNA segment to be replaced by an additional ...
In automictic parthenogenesis, meiosis takes place and diploidy is restored by fusion of first division non-sister nuclei ( ...
Diploid males tend to have a cost to the colony because diploidy can result in a reduced proportion of workers able to perform ...
It has been proposed as the basis for the emergence of the diploid phase of the life cycle as the dominant phase that diploidy ...
... because the fitness decline caused by inbreeding can be determinant in the evolution of diploidy, sexual reproduction and other ...
Diploidy without dominance Ryan, C. (1997) Diploidy without dominance. Third Nordic Workshop on Genetic Algorithms :63-70 ... Polygenic inheritanceâ A haploid scheme that can outperform diploidy Ryan, C. and Collins, J. (1998) Polygenic inheritanceâ A ... Polygenic inheritance - A haploid scheme that can outperform diploidy Ryan, C; Collins, JJ (1998) Polygenic inheritance - A ... haploid scheme that can outperform diploidy. Parallel Problem Solving from Natureâ PPSN V :178-187 ...
The advantage of diploidy, heterosis, only exists in the diploid life generation. Bryophytes retain sexual reproduction despite ... Otto, S.P.; Goldstein, D.B. (1992). "Recombination and the Evolution of Diploidy". Genetics. 131 (3): 745-751. doi:10.1093/ ...
Humans, Aneuploidy, Chromosome Aberrations, Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics, Diploidy, Chromosomal ... Diploidy; Chromosomal Instability}}, language = {{eng}}, month = {{03}}, publisher = {{Nature Publishing Group}}, series = {{ ...
2006) Genomic convergence toward diploidy in Saccharomyces cerevisiae PLOS Genetics 2:e145. ...
Novel Chromosome Organization Pattern in Actinomycetales-Overlapping Replication Cycles Combined with Diploidy. In: Mbio, Vol. ...
These abnormalities include diploidy, triploidy, and alternate sex chromosome results on placental pathology, skin biopsies, ...
... accessions with diploidy, and accessions with tetraploidy in table 3. ...
... or diploidy). Studies investigating sperm in men environmentally and/or occupationally exposed to any types of pesticides were ... and 6 studies assessing sperm aneuploidy or diploidy, of which 4 reported an association with exposure. Studies varied widely ...
Although smaller than the related Xenopus laevis, S. tropicalis has research advantages: diploidy and brief maturation time ...
We called SDs in each individual as genomic regions in which the predicted copy number significantly exceeded diploidy, while ...
Diploidy Medicine & Life Sciences 89% * Methylation Medicine & Life Sciences 74% * Fibroblasts Medicine & Life Sciences 61% ...
... whereas diploidy in the cytotrophoblastic cell line with a trisomic fetus may cause a normal discordant NIPS result [32, 42-44 ...
Diploidy: Tetraploid Flower Size & Form: 5 inches / 13cm S ... Diploidy: Tetraploid *Flower Size & Form: 5 inches / 13cm * ...
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Powered by Pure, Scopus & Elsevier Fingerprint Engine™ All content on this site: Copyright © 2024 Elsevier B.V. or its licensors and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies. For all open access content, the Creative Commons licensing terms apply We use cookies to help provide and enhance our service and tailor content. By continuing you agree to the use of cookies. ...
Powered by Pure, Scopus & Elsevier Fingerprint Engine™ All content on this site: Copyright © 2024 Elsevier B.V. or its licensors and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies. For all open access content, the Creative Commons licensing terms apply We use cookies to help provide and enhance our service and tailor content. By continuing you agree to the use of cookies. ...
The telomeres are the DNA-protein structures at the ends of eukaryotic chromosomes, which serve to protect and stabilize the genome. Normal cellular ageing involves the shortening of telomeres in each cell division. In cancer cells, the telomerase enzyme elongates telomeres, providing a mechanism for a continued unlimited cell division. Finding components that can act as inhibitors of this elongation will provide a general treatment that will be applicable to most cancer types. In our research we aim to shed light on the molecular mechanisms for the telomerase elongation and maintenance processes of telomeres. Since telomerase is recruited to and elongates the single-stranded telomeric 3′overhangs, the generation of 3′overhangs is an essential step in the maintenance process. We therefore focus on elucidating the roles of the telomere binding proteins in this process. We are using the yeast model organism Saccharomyces castellii, which has telomere traits and telomerase activity that are ...
Diploidy or not diploidy. That is the question... Ploidy Level polyploid , octoploid , hurst , x-diploid , nuclear , septet , ...
Diploidy Medicine & Life Sciences 29% * Mitochondrial DNA Medicine & Life Sciences 14% * Datasets Medicine & Life Sciences 10% ...
Diploidy Medicine & Life Sciences 32% * Genome-Wide Association Study Medicine & Life Sciences 25% ...
Heterozygosity and sex determination in haplo-diploidy. Am Nat. 1971;105:399-412. ... A heterozygous genotype in males would typically indicate diploidy. ...
Study Genetics flashcards. Play games, take quizzes, print and more with Easy Notecards.
Note that this is hard-wired for diploidy. # @param G the structure giving the genotypes of the indviduals. Actually a 3-D ... Note that this is hard-wired for diploidy. # @param G the structure giving the genotypes of the indviduals. Actually a 3-D ...
PEloid# SIAloid STYloid TABloid loidING ALKAloid AMYloidS ARILloid CHEloidS COLloidS COTYloid CYCloidS DIPloidS DIPloidY ...
Tetraploidy is probably the second most common degree of ploidy after diploidy. It has been observed in many flowering plants ... Now diploidy is again present. For the early history of the vertebrate genesis , two rounds of such genome duplications have ... Sometimes diploidy, tetraploidy and also triploidy occur in closely related species or in the same species next to each other. ...
This strategy has already been suggested [10] as it enables identification of paternal uniparental diploidy as the basis for a ... As already suggested, patients diagnosed with upd(11)pat have to be tested for paternal uniparental diploidy [10]. ... Among 254 individuals with upd(11)pat, 11 had paternal uniparental diploidy; this detection rate (4.3%) is probably an ... These include paternal uniparental diploidy (inheritance of all chromosomes from the same parent), generally presenting as ...
Otto, S.P.; Goldstein, D.B. (1992). Recombination and the Evolution of Diploidy. Genetics. 131 (3): 745-751. doi:10.1093/ ... The advantage of diploidy, heterosis, only exists in the diploid life generation. Bryophytes retain sexual reproduction despite ...
RESULTS: In FISH analysis all 48 cases of IMT showed diploidy. By immunohistochemical analysis, LIN28A expression was observed ...
Patients were classified into the following four groups based on karyotypic findings: (1) near diploidy, 42 to 47 chromosomes ( ...
  • These abnormalities include diploidy, triploidy, and alternate sex chromosome results on placental pathology, skin biopsies, and chorionic villus sampling. (medscape.com)
  • Weak relationships were found between c-myc amplification and the presence of lymph-node metastasis, advanced stage, DNA non-diploidy and premenopausal status, but not tumor size, estrogen receptor or progesterone receptor status, or int-2 amplification. (lu.se)
  • Outcomes evaluated included sperm parameters, DNA damage and numerical chromosome aberrations (aneuploidy (disomy, nullisomy) or diploidy). (cdc.gov)
  • and 6 studies assessing sperm aneuploidy or diploidy, of which 4 reported an association with exposure. (cdc.gov)
  • Flow cytometric DNA analysis of the primary tumor showed DNA aneuploidy and analysis of cultured tumor cells showed DNA diploidy indicating restricted growth of the diploid tumor cells in short-term tissue culture. (nih.gov)
  • These abnormalities include diploidy, triploidy, and alternate sex chromosome results on placental pathology, skin biopsies, and chorionic villus sampling. (medscape.com)
  • Nevertheless using diploid cells heterozygous on the mating type locus is normally difficult because they enter meiosis upon achieving stationary stage and diploidy is normally lost. (biotech-angels.com)
  • Although smaller than the related Xenopus laevis , S. tropicalis has research advantages: diploidy and brief maturation time make this species ideal for genetic analyses over multiple generations ( 2 ). (cdc.gov)
  • Fertilization of Oreochromis aureus eggs with UV-irradiated sperm from the closely related species O. niloticus, followed by diploidy restoration, produced offspring with lower embryo viability and higher skeletal deformation rates than siblings generated with sperm from a genetically distant species (Tilapia zillii). (hawaii.edu)
  • Increased tumour size and a positive nodal status predicted worse prognosis in all patients, whereas the highly correlated prognostic factors diploidy, low proliferative activity and a positive estrogen receptor status had reverse effects in mutation carriers and noncarriers. (nih.gov)