Question

In a population of mice, the presence of black spots is the result of a homozygous recessive condition. If the frequency of the allele for this condition is 0.15, what is the approximate percentage of heterozygous genotypes in this mouse population? (Assume that the population is in Hardy-Weinberg equilibrium.)
12%
26%
72%
85%

Answer 1

If A is dominant allele, and a is recessive allel, than:

p is frequency of A allele, q is a frequency of a allele, p2 is a frequency of homozygous dominant genotype, 2pq is frequency of heterozygous genotype and q2 is frequency of homozygous recessive genotype.  

If the population is in Hardy-Weinberg equilibrium; p+q=1

p=0.15 q=1-0.15=0.85

2pq=2*0.15*0.85=0.255~26%