Random Genetic Drift

Random genetic drift means random changes in genotype frequencies that result from variation in the number of offspring between individuals and (in sexual organisms) from the inherent randomness of the process of production of reproductive cells. Random genetic drift affects biological evolution in two important ways. First, it tends to remove genetic variation from populations. This is illustrated in Figure 2, using five hypothetical populations of diploid organisms each with one locus with two alleles (A and a). It is assumed that the population size is twenty individuals and that initial frequency of allele A is 0.4. In Figure 2 different lines show the dynamics of the frequency of allele A in each population. Allele frequencies fluctuate from generation to generation until genetic variation is completely lost (that is, the allele frequency becomes equal to one or zero). Under random genetic drift, this happens in a time span comparable with the population size. Second, random genetic drift affects the probability of survival of new mutations in the population (see the section on natural selection, below). The effects of random genetic drift are inversely proportional to the population size, so that it is most important in small populations and is negligible in large populations. If mutation and random genetic drift are the only forces acting on a population, the population will continuously accumulate new mutations with the rate equal exactly to the mutation rate.

Worm Farming

Worm Farming

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