The principle is that sum total of all allelic frequencies is 1.
Individual frequencies for example can be named p,q.In a diploid cell , p and q represent the frequency of allele A and a respectively . The frequency of AA individuals in a population is p2 as the probability of an allele A with a frequency of p appear on both the chromosomes of a diploid individual is simply the product of the probabilities. Similarly for aa it will be q2.Can anybody explain that how it will be 2pq for Aa?
I am getting it as pq.