Question

If the allele frequencies of b and B are 0.25 and 0.75 (respectively) what will be the frequency of heterozygotes after one round of random mating (i.e., allele frequencies in the next generation)?
Also, what is the frequency of the homozygote bb in the next generation?

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Answer 1

The frequency of homozygotes and heterozygotes in the next generation can be predicted by using the Hardy-Weinberg principle. which applies basic rules of probability to a population to make predictions about the next generation. The Hardy-Weinberg principle predicts that allelic frequencies remain constant from one generation to the next, or remain in EQUILIBRIUM, if we assume certain conditions.

According to this principle,

p + q = 1 or

p² + q² + 2pq = 1

where, p = frequency of the dominant allele

q= frequency of the recessive allele

p² and q² = frequency of dominant and recessive homozygotes respectively.

2pq = frequency of heterozygotes.

According to the question, frequencies recessive (b = q) and dominant (B=p) alleles are given as 0.25 and 0.75 respectively.

Therefore, frequency of heterozygotes in the next generation after one round of random mating will be = 2pq

2pq = 2 x 0.25 x 0.75 = 0.375

Also, frequency of recessive homozygote (bb) will be = q² = 0.25 x 0.25 = 0.0625