Question

A population of cats has 120 black individuals (BB genotype), 45 brown individuals (Bb) and 25 light brown individuals (bb). Use the method of counting the number of alleles to determine the gene frequency

Answer 1

The genotype frequency is calculated by Hardy Weinberg equation i-e p²+2(pq)+q²=1

As per given data q²=bb=25 or q=square root of 25 =5

Or we say q allele contributes some percent to population, therfore q=5/100=0.05

Now, p=1-q or 1-0.05=0.95

Substituting the value of p and q in Hardy Weinberg equation we get: 0.95²+2(.95*.05)+0.05²

Or the frequency of the genotype BB=,0.95² = 0.90

The frequency of heterozygotes Bb= 2(0.95x0.05)=0.9

The frequency of Homozygous recessive bb=0.05²=0.0025