Question

Does the following fitness array reflect heterozygote inferiority or superiority?

                                  A1A1               A1A2                   A2A2

fitness              0.70                 1                      0.80

Calculate the equilibrium frequency of p for the given fitnesses.

Is this a stable or unstable equilibrium?

Answer 1

The given relative fitness values are:

A1A1, W11 = 0.70

A1A2, W12 = 1.0

A2A2, W22 = 0.80

Here the relative fitness of heterozygous genotype, A1A2, is highest. Thus, the data shows heterozygote superiority.

Equilibrium frequency of allele p can be calculated as:

=( W22 - W12) / ( W11 - 2W12 + W22)

= (0.80-1) /(0.70 - 2 + 0.80)

= (-0.20) /(-0.50)

= 0.4

Equilibrium frequency of allele p = 0.4 .

This is a stable equilibrium, as equilibrium frequency of p is between 0 and 1.

Unstable equilibrium arises when equilibrium frequency of an allele becomes 0 or 1.