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Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, [1] is the change in the frequency of an existing gene variant in a population due to random chance. [ 2 ] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation . [ 3 ]
Hence the name "drifty" genes, to contrast the positively selected "thrifty genes". Such drift may have started because around 2 million years ago when ancestral humans effectively removed the risk of predation, which was probably a key factor maintaining the upper boundary of the regulation system.
Neutral drift is the idea that a neutral mutation can spread throughout a population, so that eventually the original allele is lost. A neutral mutation does not bring any fitness advantage or disadvantage to its bearer. The simple case of the Moran process can describe this phenomenon.
Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal mechanism underlying speciation. On a molecular genetics level, genetic divergence is due to changes in a small number of genes in a species, resulting in speciation . [ 2 ]
Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion. [ 5 ] Rapid sympatric speciation can take place through polyploidy , such as by doubling of chromosome number; the result is progeny which are immediately reproductively isolated from the parent population.
For instance, if divergence is due to different selection pressures, thus causing natural selection to act, or to random genetic drift. [12] Therefore, Dobzhansky–Muller incompatibilities can also provide information on the time and type of divergence which can help in phylogenetic studies.
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Coalescent theory is a model of how alleles sampled from a population may have originated from a common ancestor.In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structure, meaning that each variant is equally likely to have been passed from one generation to the next.