In a population, the frequency of the genotype AA at a single nucleotide polymorphism (SNP) locus is 64%, AG is 32%, and GG is 4%. What is the frequency of the allele A?
Correct answer: D. 0.8
The frequency of the allele A can be calculated as (2 * frequency of AA + frequency of AG) / 2 = (2 * 0.64 + 0.32) / 2 = 0.8.