Question

Suppose alleles A1,A2,A3, and A4 are additive in their effects, and the homozygote fitnessesare A1A1: 0.8, A2A2: 0.6, A3A3: 0.4, and A4A4: 0.2. What are the heterozygote fitnesses? I fall of the alleles are of equal frequency, what is the mean fitness for this locus?

Answer 1

As the alleles are additive and provided homozygote fitness

A1A1 = 0.8

  A2A2 = 0.6

  A3A3 = 0.4

  A4A4 = 0.2

Heterozygotes will be A1A2, A1A3, A1A4, A2A3, A2A4, A3A4

  A1A2 = 0.8/2 x 0.6/2 = 0.12

  A1A3 = 0.8/2 x 0.4/2 = 0.08

  A1A4 =0.8/2 x 0.2/2 = 0.04

  A2A3 =0.6/2 x 0.4/2 = 0.06

  A2A4 =0.6/2 x 0.2/2 =0.03

  A3A4 = 0.4/2 x 0.2/2 =0.02

Mean fitness for this locus = (0.8/2 + 0.6/2 + 0.4/2 + 0.2/2)/4 =1/4= 0.25