. Industrial melanism refers to the dark pigmentation that evolved in some insec

Question

. Industrial melanism refers to the dark pigmentation that evolved in some insects giving them protective coloration on vegetation darkened by soot in heavily industrialized areas prior to air pollution regulation. In one heavily polluted area near Birmingham, England in 1956, 79% of the moths of the species Biston betularia were black due to the presence of a dominant gene for melanism. Estimate both the frequency of the dominant allele in this population, and the proportion of black moths that are heterozygous (note: that’s heterozygotes out of black moths, not out of total moths). Show your work.

Explanation / Answer

If B is the dominant allele, then 21% of the white moths were homozygous recessive that is bb. Therefore, 21% or 0.21 had the genotype of bb. If frequency of bb = 0.21, then the frequency of b = sqrt(0.21) = 0.4583.
Therefore, frequency of B = 1-0.4583 = 0.5417.
So, the frequency of heterozygotes = 2(0.4583)(0.5417) = 0.4965

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