The gametic frequencies of a population at two loci are in the following manner:
• AB = 0.40
• Ab = 0.1
• aB = 0.1
• ab = 0.4
When the population is allowed to mate until linkage equilibrium occurs, there will be an equal proportion of both the alleles on both chromosomes.
The frequency of B allele on chromosome A is 0.4 and frequency of B on chromosome a is 0.1. The equilibrium value would be 0.25. So, the frequency of Ab and aB would be 0.25. Since both these genotypes are heterozygous, the expected frequencies would be 0.25, if the linkage equilibrium occurs for this pair of genes.
So, the frequency of each locus would be 0.5. Hence, p and q are 0.5. The frequency of A or a is 0.5 and the frequency of B or b is also 0.5. The frequency of 2pq would be 0.5.
At linkage equilibrium, the frequency of heterozygotes for both the alleles will be the multiplication product of their individual frequencies of 0.5 x 0.5 = 0.25.