Question

Suppose a population is carrying a condition controlled by two alleles: P (dominant) and p (recessive). Only homozygous individuals that have two copies of the recessive allele have the condition. If the p allele is found in 15 percent of the population, what's the frequency of the PP genotype?

Answer 1

If we know that we have Pp PP and pp individuals.

Only homozygous individuals that have two coies of the recessive allele have the conditions - 15%
If we know that the p allele itself is found in 15% of the population. 

We know that the P allele is found in 75% of the population (100 - 15)

To now know what is the frequency of the PP genotype, we can calculate this using simple mathematics:

If P is now 75%, to get 2x P we have to calculate 75%*75% =56.25%

So an individual who is of the genotype PP can be most likely found with the frequency of around 60% in this population.