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In biology, a mutation is an alteration in the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA, which then may undergo error-prone repair, cause an error during other forms of repair, or cause an error during replication. Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements.
A somatic cell, or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell.
The term somatic - etymologically from the French word "somatique", from Ancient Greek "σωματικός", from σῶμα - is often used in biology to refer to the cells of the body in contrast to the reproductive (germline) cells, which usually give rise to the egg or sperm. These somatic cells are diploid, containing two copies of each chromosome, whereas germ cells are haploid, as they only contain one copy of each chromosome. Although under normal circumstances all somatic cells in an organism contain identical DNA, they develop a variety of tissue-specific characteristics. This process is called differentiation, through epigenetic and regulatory alterations. The grouping of similar cells and tissues creates the foundation for organs.
Carcinoma is a malignancy that develops from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesodermal or ectodermal germ layer during embryogenesis.
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult, such as the floral meristem of flowering plants.
In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They are usually differentiated to perform this function and segregated in a specific place away from other bodily cells.
Mosaicism or genetic mosaicism is a condition in multi-cellular organisms in which a single organism possesses more than one genetic line as the result of genetic mutation. This means that various genetic lines resulted from a single fertilized egg. Genetic mosaics may often be confused with chimerism, in which two or more genotypes arise in one individual similarly to mosaicism. In chimerism, though, the two genotypes arise from the fusion of more than one fertilized zygote in the early stages of embryonic development, rather than from a mutation or chromosome loss.
In genetics, genotoxicity describes the property of chemical agents that damages the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, whereas not all genotoxic substances are mutagenic. The alteration can have direct or indirect effects on the DNA: the induction of mutations, mistimed event activation, and direct DNA damage leading to mutations. The permanent, heritable changes can affect either somatic cells of the organism or germ cells to be passed on to future generations. Cells prevent expression of the genotoxic mutation by either DNA repair or apoptosis; however, the damage may not always be fixed leading to mutagenesis.
A germline mutation, or germinal mutation, is any detectable variation within germ cells. Mutations in these cells are the only mutations that can be passed on to offspring, when either a mutated sperm or oocyte come together to form a zygote. After this fertilization event occurs, germ cells divide rapidly to produce all of the cells in the body, causing this mutation to be present in every somatic and germline cell in the offspring; this is also known as a constitutional mutation. Germline mutation is distinct from somatic mutation.
Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and secondary spermatocytes. Primary and secondary spermatocytes are formed through the process of spermatocytogenesis.
Genetics, a discipline of biology, is the science of heredity and variation in living organisms.
Enquiry into the evolution of ageing, or aging, aims to explain why a detrimental process such as ageing would evolve, and why there is so much variability in the lifespans of organisms. The classical theories of evolution suggest that environmental factors, such as predation, accidents, disease, starvation, ensure that most organisms living in natural settings will not live until old age, and so there will be very little pressure to conserve genetic changes that increase longevity. Natural selection will instead strongly favor genes which ensure early maturation and rapid reproduction, and the selection for genetic traits which promote molecular and cellular self-maintenance will decline with age for most organisms.
The cells that give rise to the gametes are often set aside during embryonic cleavage. During development, these cells will differentiate into primordial germ cells, migrate to the location of the gonad, and form the germline of the animal.
This glossary of genetics is a list of definitions of terms and concepts commonly used in the study of genetics and related disciplines in biology, including molecular biology and evolutionary biology. It is intended as introductory material for novices; for more specific and technical detail, see the article corresponding to each term. For related terms, see Glossary of evolutionary biology.
G-protein coupled receptor 3 is a protein that in humans is encoded by the GPR3 gene. The protein encoded by this gene is a member of the G protein-coupled receptor family of transmembrane receptors and is involved in signal transduction.
Acute megakaryoblastic leukemia (AMKL) is life-threatening leukemia in which malignant megakaryoblasts proliferate abnormally and injure various tissues. Megakaryoblasts are the most immature precursor cells in a platelet-forming lineage; they mature to promegakaryocytes and, ultimately, megakaryocytes which cells shed membrane-enclosed particles, i.e. platelets, into the circulation. Platelets are critical for the normal clotting of blood. While malignant megakaryoblasts usually are the predominant proliferating and tissue-damaging cells, their similarly malignant descendants, promegakaryocytes and megakaryocytes, are variable contributors to the malignancy.
A knockout rat is a genetically engineered rat with a single gene turned off through a targeted mutation used for academic and pharmaceutical research. Knockout rats can mimic human diseases and are important tools for studying gene function and for drug discovery and development. The production of knockout rats was not economically or technically feasible until 2008.
The disposable soma theory of aging states that organisms age due to an evolutionary trade-off between growth, reproduction, and DNA repair maintenance. Formulated by Thomas Kirkwood, the disposable soma theory explains that an organism only has a limited amount of resources that it can allocate to its various cellular processes. Therefore, a greater investment in growth and reproduction would result in reduced investment in DNA repair maintenance, leading to increased cellular damage, shortened telomeres, accumulation of mutations, compromised stem cells, and ultimately, senescence. Although many models, both animal and human, have appeared to support this theory, parts of it are still controversial. Specifically, while the evolutionary trade-off between growth and aging has been well established, the relationship between reproduction and aging is still without scientific consensus, and the cellular mechanisms largely undiscovered.
Pig-a gene mutation assay is a flow cytometry-based method for detecting mammalian cells that have inactivating mutations in the endogenous X-linked reporter gene called phosphatidyl inositolglycan class A gene. PIG-A is involved in the synthesis of glycosylphosphatidylinositol (GPI), an anchor molecule that tethers multiple protein marker molecules at the surface of the cells. When the sample containing wild-type and PIG-A mutant cells is labeled with fluorescent antibodies raised against GPI-anchored protein markers the wild-type cells will fluoresce and PIG-A mutant cells will not. The fraction of non-fluorescent PIG-A mutant cells in the antibody-labeled sample can be efficiently determined on any of the modern high throughput flow cytometers. The PIG-A mutant frequency can be determined with high accuracy within minutes by processing samples containing a total of a million cells or more.
A somatic mutation is a change in the DNA sequence of a somatic cell of a multicellular organism with dedicated reproductive cells; that is, any mutation that occurs in a cell other than a gamete, germ cell, or gametocyte. Unlike germline mutations, which can be passed on to the descendants of an organism, somatic mutations are not usually transmitted to descendants. This distinction is blurred in plants, which lack a dedicated germline, and in those animals that can reproduce asexually through mechanisms such as budding, as in members of the cnidarian genus Hydra.
References
- ↑ Araten, D., Golde, D., Zhang, R., Taler, H., Gargiulo, L., Notaro, G., & Luzzatto, L. (2005). A quantitative measurement for the human somatic mutation rate. Cancer Research, (65), 8111-8117.
- ↑ Peruzzi, B., Araten, D., Notaro, R., & Luzzatto, L. (2009). The use of pig-a as a sentinel gene for the study of the somatic mutation rate and the mutagenic agents in vivo. Mutation Research, (705), 3-10.
- ↑ Peruzzi, B., Araten, D., Notaro, R., & Luzzatto, L. (2009). The use of pig-a as a sentinel gene for the study of the somatic mutation rate and the mutagenic agents in vivo. Mutation Research, (705), 3-10.described mutation frequency as containing a segment of cells that includes a mutation within particular trait, and the authors defined mutation rates as being chances a innovative alteration will take place in hereditary trait due to cell division.
- ↑ Clune, J., Misevic, D., Ofria, C., Lenski, R., Elena, S. F., & Sanjuan, R. (2008). Natural selection fails to optimize mutation rates for long-term adaptation on rugged fitness landscapes. Computational Biology, 4(9), 1-8.
- 1 2 Nishant, K., Singh, N., & Alani, E. (2009). Genomic mutation rates: what high-throughput methods can tell us. Bioessays, 31(9), 912-920.
- ↑ Yoon, S., Qin, J., Glaser, R., Jabs, E., Wexler, N., Sokol, R., Arnheim, N., & Calabrese, P. (2009). The ups and downs of mutation frequencies during aging can account for the apert syndrome paternal age effect. PLos Genetics, 5(7), 1-19.
- ↑ http://users.rcn.com./jkimball.ma.ultranet/BiologyPages/M/Mutations.html(http://users.rcn.com./jkimball.ma.ultranet/BiologyPages/M/Mutations.html) [ dead link ]
- 1 2 Hill KA, Halangoda A, Heinmoeller PW, Gonzalez K, Chitaphan C, Longmate J, Scaringe WA, Wang JC, Sommer SS. Tissue-specific time courses of spontaneous mutation frequency and deviations in mutation pattern are observed in middle to late adulthood in Big Blue mice. Environ Mol Mutagen. 2005 Jun;45(5):442-54. doi: 10.1002/em.20119. PMID 15690342
- ↑ Stuart GR, Oda Y, Boer JG, Glickman BW. No change in spontaneous mutation frequency or specificity in dietary restricted mice. Carcinogenesis. 2000 Feb;21(2):317-9. doi: 10.1093/carcin/21.2.317. PMID 10657975