Assume there is a Mendelian trait determined by two alleles

Assume there is a Mendelian trait determined by two alleles, A and a. The allele frequencies in the population are AJ0.8, a 0.2. Assuming that there is no immediate selection on this trait, what are the genotype frequencies in a population of 500 individuals? How many individuals with each genotype are there?

Solution

Here allele frequency of two alleles \"A\" and \"a\" is ;

A = 0.8 and a = 0.2.

These two alleles can form three genotypes viz;

AA , aa and Aa.

Genotypic frequency can be calculated as ;

f (AA) = (0.8)^2 = 0.64

f(aa) = (0.2)^2 = 0.04.

f (Aa) = 2 × 0.8 ×0.2 = 0.32.

Genotypic frequency in the population of 500 individuals is

AA = 500 × 0.64 = 320.

Therefore there are total of 320 individuals with genotype AA

Genotypic frequency f(AA) will be 320/500 = 0.64.

aa = 500 × 0.04 = 20.

Total number of individuals with genotype aa = 20.

Genotypic frequnecy will be 20/ 500 = 0.04.

Aa = 500 × 0.32 = 160.

Thereforw total number of individuals with genotype Aa = 160.

Genotypic frequency = 160/500 = 0.32.