See the blue underlined part.
Now please explain me why did the probability of 'Aa' be "2pq".
Where the "2" come from? It should have been only (pq), isn't it?
Dear Student,
As you know,
Sum total of all allelic frequencies is 1.
'p' & 'q' represent the individual frequency of alleles A & a respectively. If these two alleles are present on the same locus and the random mating occurs then the possible genotype of the offsprings would be either- 'AA' i.e p2 or 'aa' i.e q2 or 'Aa' i.e 2pq. Thus, 2pq represent that the offspring is not homozygous rather it is heterozygous having both the alleles A & a.
Regards