The transient distribution of allele frequencies under mutation pressure

Abstract

SUMMARYThe transient distribution of allele frequencies in a finite population is derived under the assumption that there arekpossible alleic states at a locus and mutation occurs in all directions. At steady state this distribution becomes identical with the distribution obtained by Wright, Kimura and Crow whenk= ∞. The rate of approach to the steady state distribution is generally very slow, the asymptotic rate being 2v+ 1/(2N), wherevandNare the mutation rate and effective population size, respectively. Using this distribution it is shown that when population size is suddenly increased, the expected number of alleles increases more rapidly than the expected heterozygosity. Implications of the present study on testing hypotheses for the maintenance of genetic variability in populations are discussed.