Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype, or the presence of genotypically different individuals, in contrast to environmentally induced differences which, as a rule, cause only temporary, nonheritable changes of the phenotype".[1] Genetic variability in a population is important for biodiversity.[2]
There are many sources of genetic variability in a population:
Homologous recombination is a significant source of variability. During meiosis in sexual organisms, two homologous chromosomes cross over one another and exchange genetic material. The chromosomes then split apart and are ready to contribute to forming an offspring. Recombination is random[citation needed] and is governed by its own set of genes. Being controlled by genes means that recombination is variable in frequency.
Immigration, emigration, and translocation – each of these is the movement of an individual into or out of a population. When an individual comes from a previously genetically isolated population into a new one it will increase the genetic variability of the next generation if it reproduces.[3]
Polyploidy – having more than two homologous chromosomes allows for even more recombination during meiosis allowing for even more genetic variability in one's offspring.
Diffuse centromeres – in asexual organisms where the offspring is an exact genetic copy of the parent, there are limited sources of genetic variability. One thing that increased variability, however, is having diffused instead of localized centromeres. Being diffused allows the chromatids to split apart in many different ways allowing for chromosome fragmentation and polyploidy creating more variability.[4]
Genetic mutations – contribute to the genetic variability within a population and can have positive, negative, or neutral effects on a fitness.[5] This variability can be easily propagated throughout a population by natural selection if the mutation increases the affected individual's fitness and its effects will be minimized/hidden if the mutation is deleterious. However, the smaller a population and its genetic variability are, the more likely the recessive/hidden deleterious mutations will show up causing genetic drift.[5]
DNA damages are very frequent, occurring on average more than 60,000 times a day per cell in humans due to metabolic or hydrolytic processes as summarized in DNA damage (naturally occurring). Most DNA damages are accurately repaired by various DNA repair mechanisms. However, some DNA damages remain and give rise to mutations.
It appears that most spontaneously arising mutations result from error prone replication (trans-lesion synthesis) past a DNA damage in the template strand. For example, in yeast more than 60% of spontaneous single-base pair substitutions and deletions are likely caused by translesion synthesis.[6] Another significant source of mutation is an inaccurate DNA repair process, non-homologous end joining, that is often employed in repair of DNA double-strand breaks.[7] (Also see Mutation.) Thus it seems that DNA damages are the underlying cause of most spontaneous mutations, either because of error-prone replication past damages or error-prone repair of damages.
Factors that decrease genetic variabilityedit
There are many sources that decrease genetic variability in a population:
Habitat loss, including:
Habitat fragmentation produces discontinuity in an organism's habitat, so that interbreeding is limited. Fragmentation can be caused by many factors, including geological processes or a human-caused events. Fragmentation may further allow genetic drift to lower local genetic diversity.
Climate change is a drastic and enduring change in weather patterns. By driving species out of their fundamental niche, climate change can lower population size and consequently lower genetic variation.
The founder effect, which occurs when a population is founded by few individuals.
^Rieger, R.; Michaelis, A.; Green, M.M. (1968), A glossary of genetics and cytogenetics: Classical and molecular, New York: Springer-Verlag, ISBN9780387076683
^Sousa, P., Froufe, E., Harris, D.J., Alves, P.C. & Meijden, A., van der. 2011. Genetic diversity of Maghrebian Hottentotta (Scorpiones: Buthidae) scorpions based on CO1: new insights on the genus phylogeny and distribution. African Invertebrates52 (1).. Archived from the original on 2011-10-04. Retrieved 2011-05-03.{{cite web}}: CS1 maint: archived copy as title (link)
^Ehrich, Dorothy; Per Erik Jorde (2005). "High Genetic Variability Despite High-Amplitude Population Cycles in Lemmings". Journal of Mammalogy. 86 (2): 380–385. doi:10.1644/BER-126.1.
^Linhart, Yan; Janet Gehring (2003). "Genetic Variability and its Ecological Implications in the Clonal Plant Carex scopulurum Holm. In Colorado Tundra". Arctic, Antarctic, and Alpine Research. 35 (4): 429–433. doi:10.1657/1523-0430(2003)035[0429:GVAIEI]2.0.CO;2. ISSN 1523-0430. S2CID 86464133.
^ abWills, Christopher (1980). Genetic Variability. New York: Oxford University Press. ISBN978-0-19-857570-2.
^Kunz BA, Ramachandran K, Vonarx EJ (April 1998). "DNA sequence analysis of spontaneous mutagenesis in Saccharomyces cerevisiae". Genetics. 148 (4): 1491–505. doi:10.1093/genetics/148.4.1491. PMC1460101. PMID 9560369.
^Huertas P (January 2010). "DNA resection in eukaryotes: deciding how to fix the break". Nat. Struct. Mol. Biol. 17 (1): 11–6. doi:10.1038/nsmb.1710. PMC2850169. PMID 20051983.
December 15, 2023
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Genetic variability is either the presence of or the generation of genetic differences It is defined as the formation of individuals differing in genotype or the presence of genotypically different individuals in contrast to environmentally induced differences which as a rule cause only temporary nonheritable changes of the phenotype 1 Genetic variability in a population is important for biodiversity 2 Contents 1 Causes 2 Factors that decrease genetic variability 3 See also 4 ReferencesCauses editThere are many sources of genetic variability in a population Homologous recombination is a significant source of variability During meiosis in sexual organisms two homologous chromosomes cross over one another and exchange genetic material The chromosomes then split apart and are ready to contribute to forming an offspring Recombination is random citation needed and is governed by its own set of genes Being controlled by genes means that recombination is variable in frequency Immigration emigration and translocation each of these is the movement of an individual into or out of a population When an individual comes from a previously genetically isolated population into a new one it will increase the genetic variability of the next generation if it reproduces 3 Polyploidy having more than two homologous chromosomes allows for even more recombination during meiosis allowing for even more genetic variability in one s offspring Diffuse centromeres in asexual organisms where the offspring is an exact genetic copy of the parent there are limited sources of genetic variability One thing that increased variability however is having diffused instead of localized centromeres Being diffused allows the chromatids to split apart in many different ways allowing for chromosome fragmentation and polyploidy creating more variability 4 Genetic mutations contribute to the genetic variability within a population and can have positive negative or neutral effects on a fitness 5 This variability can be easily propagated throughout a population by natural selection if the mutation increases the affected individual s fitness and its effects will be minimized hidden if the mutation is deleterious However the smaller a population and its genetic variability are the more likely the recessive hidden deleterious mutations will show up causing genetic drift 5 DNA damages are very frequent occurring on average more than 60 000 times a day per cell in humans due to metabolic or hydrolytic processes as summarized in DNA damage naturally occurring Most DNA damages are accurately repaired by various DNA repair mechanisms However some DNA damages remain and give rise to mutations It appears that most spontaneously arising mutations result from error prone replication trans lesion synthesis past a DNA damage in the template strand For example in yeast more than 60 of spontaneous single base pair substitutions and deletions are likely caused by translesion synthesis 6 Another significant source of mutation is an inaccurate DNA repair process non homologous end joining that is often employed in repair of DNA double strand breaks 7 Also see Mutation Thus it seems that DNA damages are the underlying cause of most spontaneous mutations either because of error prone replication past damages or error prone repair of damages Factors that decrease genetic variability editThere are many sources that decrease genetic variability in a population Habitat loss including Habitat fragmentation produces discontinuity in an organism s habitat so that interbreeding is limited Fragmentation can be caused by many factors including geological processes or a human caused events Fragmentation may further allow genetic drift to lower local genetic diversity Climate change is a drastic and enduring change in weather patterns By driving species out of their fundamental niche climate change can lower population size and consequently lower genetic variation The founder effect which occurs when a population is founded by few individuals See also editEvolvability Human genetic variation Personalized medicineReferences edit Rieger R Michaelis A Green M M 1968 A glossary of genetics and cytogenetics Classical and molecular New York Springer Verlag ISBN 9780387076683 Sousa P Froufe E Harris D J Alves P C amp Meijden A van der 2011 Genetic diversity of Maghrebian Hottentotta Scorpiones Buthidae scorpions based on CO1 new insights on the genus phylogeny and distribution African Invertebrates 52 1 Archived copy Archived from the original on 2011 10 04 Retrieved 2011 05 03 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Ehrich Dorothy Per Erik Jorde 2005 High Genetic Variability Despite High Amplitude Population Cycles in Lemmings Journal of Mammalogy 86 2 380 385 doi 10 1644 BER 126 1 Linhart Yan Janet Gehring 2003 Genetic Variability and its Ecological Implications in the Clonal Plant Carex scopulurum Holm In Colorado Tundra Arctic Antarctic and Alpine Research 35 4 429 433 doi 10 1657 1523 0430 2003 035 0429 GVAIEI 2 0 CO 2 ISSN 1523 0430 S2CID 86464133 a b Wills Christopher 1980 Genetic Variability New York Oxford University Press ISBN 978 0 19 857570 2 Kunz BA Ramachandran K Vonarx EJ April 1998 DNA sequence analysis of spontaneous mutagenesis in Saccharomyces cerevisiae Genetics 148 4 1491 505 doi 10 1093 genetics 148 4 1491 PMC 1460101 PMID 9560369 Huertas P January 2010 DNA resection in eukaryotes deciding how to fix the break Nat Struct Mol Biol 17 1 11 6 doi 10 1038 nsmb 1710 PMC 2850169 PMID 20051983 Retrieved from https en wikipedia org w index php title Genetic variability amp oldid 1152068961, wikipedia, wiki, book, books, library,
