Question

Genetic Makeup of a Mouse Population

Genotype	Phenotype	Number of Individuals in Original Population	Number of Individuals in New Population
BB	Brown	841	841
Bb	Tan	1218	1218
bb	Gray	441	0
Total		2500	2059

The genetic makeup of a mouse population is provided in the table above. At the start of an experiment, researchers remove all the gray mice from the population, resulting in a population that is not in Hardy-Weinberg equilibrium. Calculate the frequency of the recessive allele in the remaining population of mice. Give your answer as a decimal to two places.

Answer 1

Allele frequency is the frequency of any given allele in a population, relative to all the other alleles at same locus. It is calculated by the formula -

Allele frequency = No. of copies of a particular allele / Total no. of all alleles for that gene in a population

Since a homozygote carries two copies of an allele, we multiply the no. of homozygotes by 2.

In this case, population of homozygotes for gray phenotype is 0.

Allele frequency of recessive allele "b" in the remaining population = (2*0 + 1218) / 2*2059 = 1218 / 4118 = 0.30