Effects of Selection and Drift on the Dynamics of Finite Populations. I. Ultimate Probability of Fixation of a Favorable Allele

In a finite population with one locus and two alleles, selection, in the absence of overdominance, increases the probability of ultimate fixation of the favorable allele (fe). For any selection intensity (s) there is an initial gene frequency, X' below which f, is ail increasing function of the degree of dominance (h) and above which it is a decreasing function of h. X' is also an increasing function of the selection intensity. For overdominance (h > l)fi is less than in the case of no selection when the initial gene frequency is above a certain value X". The point X" is a decreasing function of h and an increasing function of the selection intensity. For both dominance and overdominance f, is a strictly increasing function of the initial gene frequency.