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Question
How is Hardy-Weinberg’s expression “(p2 + 2pq + q2) = 1” derived?
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Solution
Sum total of all the allelic frequencies is 1. Let there be two alleles A and a in a population. The frequencies of alleles A and a are ‘p’ and ‘q’ respectively.
The frequency of AA individuals in a population is p2 and it can be explained that the probability that an allele A with a frequency of p would appear on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e., p2.
Similarly, the frequency of aa is q2 and that of Aa is 2pq.
(p2 + 2pq + q2) = 1 where p2 represents the frequency of the homozygous dominant genotype, 2pq represents the frequency of the heterozygous genotype and q2 represents the frequency of the homozygous recessive.
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