NS
        07 Box6

Alternative calculation of equilibrium allele frequency () under heterozygote advantage
("Overdominance")

Note that the top line is equivalent to (p)() = W0p2 + W1(pq)
which reduces to the final

sAAfA = saafa

which can be written in terms of s coefficients and q as

(s1)(1-q) = (s2)(q)

s1 - s1q = s2q

s1 = s2q + s1q

s1 = (s2 + s1)(q)

(s1)) / (s2 + s1)q =


    "Overdominance" is an unfortunate term, as 'dominance' is a relationship among alleles at a locus, but is applied here to describe the fitness phenotype of the Aa genotype, relative to that of the AA and aa genotypes. The companion term "underdominance" to describe heterozygote disadvantage creates the same problem. Like use of  'gene' when we mean 'allele', the latter terms are too well established to discard outright, but should be avoided where possible.

Figure © 2013 by Sinauer; Text material © 2024 by Steven M. Carr