At the start of this drift process in our array of populations, p = 0.5 and there are 2pq = 0.5 = 50% heterozygotes. When all populations in the array have fixed or lost the allele, there can be no heterozygotes (i.e., 0%). This shows that the proportion of heterozygotes decreases as drift proceeds (this also occurs when there is inbreeding which can also be thought of as a sampling error phenomenon). We can quantify this process as follows: the proportion of heterozygotes in the "next " generation is a function of the proportion of heterozygotes in the present generation and the "rate" at which drift proceeds: H t+1 = H t [1 - (1/2N)] where H = the proportion of heterozygotes in the population (or in the array of populations) and N = population size. This can be extended over many generations as follows: H t = H0 [1 - (1/2N)] t where t refers to the number of generations in the future and 0 refers to the present (or starting) generation. Looking at these equations it is clear that with small population sizes, heterozygosity
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