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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
= H
0
[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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 Fall '10
 JessicaDigirolamo
 Microbiology, Zygote

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