Question

Feather color in these gulls is due to variation at the M- locus. Black colord birds are either MM or Mm, white birds are mm. On each of the islands, assume that the gull population contains approximately 190 black colored (melanic) individuals and 810 white individuals. Assuming hardy weinberg equilibrium. what is the frequency of the M allele in each population

Answer 1

There are two important equations with Hardy-Weinberg: R + r = 1 and R^2 + 2Rr + r^2 = 1. In this case, R^2 refers to the MM genotype, 2Rr refers to the Mm genotype, and r^2 is the mm genotype. All of the white individuals are rr, because white is recessive. So, r^2 = 810/1000 or 0.81 (there are 1000 total individuals). After doing the square root, we will find that r = 0.90. As we know, R + r = 1. So if r = 0.9 then R = 1 - 0.9 = 0.1. So, only 0.1 (10%) of the chromosomes are carrying the dominant M allele.