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Nearly neutral mutations are those that carry selection coefficients less than the inverse of twice the effective population size. [30] The population dynamics of nearly neutral mutations are only slightly different from those of neutral mutations unless the absolute magnitude of the selection coefficient is greater than 1/N, where N is the ...
In population genetics and population ecology, population size (usually denoted N) is a countable quantity representing the number of individual organisms in a population. Population size is directly associated with amount of genetic drift , and is the underlying cause of effects like population bottlenecks and the founder effect . [ 1 ]
The nearly neutral theory was proposed by Tomoko Ohta in 1973. [2] The population-size-dependent threshold for purging mutations has been called the "drift barrier" by Michael Lynch, and used to explain differences in genomic architecture among species.
The effective population size (N e) is the size of an idealised population that would experience the same rate of genetic drift as the real population. [1] Idealised populations are those following simple one-locus models that comply with assumptions of the neutral theory of molecular evolution.
Under the neutral theory model, for a population at constant size at equilibrium: [] = = [=] =for diploid DNA, and [] = = [=] =for haploid. In the above formulas, S is the number of segregating sites, n is the number of samples, N is the effective population size, is the mutation rate at the examined genomic locus, and i is the index of summation.
The Neutral Theory of Molecular Evolution is an influential monograph written in 1983 by Japanese evolutionary biologist Motoo Kimura.While the neutral theory of molecular evolution existed since his article in 1968, [1] Kimura felt the need to write a monograph with up-to-date information and evidences showing the importance of his theory in evolution.
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.
They determined that in the neutral case, the probability that an individual would be homozygous, F, was: = + where u is the mutation rate, and N e is the effective population size. The effective number of alleles n maintained in a population is defined as the inverse of the homozygosity, that is