Coat coloration in New Mexico Desert mice is controlled by t

Coat coloration in New Mexico Desert mice is controlled by the D locus with two alleles with D completely dominant to d; DD and Dd individuals have dark coloration whereas dd individuals have lighter coloration. You observe a population with 800 individuals with genotype DD, 500 individuals with genotype Dd, and 80 dd individuals

a.What are the genotype and allele frequencies in this population?

b.You determined the survival of these genotypes on dark lava rock habitats during the spring when predator activity was high. The number of individuals is given below. Determine the relative fitness (w) and selection coefficient (s) for each genotype

                                    DD = 400        Dd = 250        dd = 25

c.Calculate the normalized genotype frequencies after selection

d.Calculate the allele frequencies after selection. What happened to the frequency of the D and d allele? Why? Is this form of directional selection dominant or codominance? If you answered dominant, would the change in allele frequency be greater if this were codominance? If yes, why?

Solution

The population we analysed has two alleles, so total number of alleles are 1380X2= 2760 allele. To determine allelic frequencies, we count D and d alleles and divide by total number of alleles.

f(D)= [(2 X800) +500] / 2760 = 0.76

f(d)= [(2 X 80) + 500] / 2760 = 0.23