Calculating genotype frequencies

Once you know the allele frequencies you can calculate the expected genotype frequencies using those values (the values given here for p and q are from the topic on calculating allele frequencies).

Frequency of homozygous dominant = p² = 0.449² =   0.202

Frequency of heterozygous = 2pq = 2 x 0.449 x 0.551 = 0.495

Frequency of homozygous recessive = q² = 0.551² = 0.304

We often find that genetic diseases are recessive, and only expressed in the homozygous recessive form. In such a case, the heterozygous individuals would be called "carriers" because they can pass the disease gene to their offspring, but they usually don't have the disease. These genotype frequencies are going to be worthwhile in their own right, but mostly because they can be used for the calculations to see if the H-W equation applies to a particular population.