Answer:
C. homozygous recessive
Step-by-step explanation:
In a certain trait determined by one gene with two alleles, the possible genotypes and phenotypes are:
- AA: homozygous dominant, A_ phenotype.
- Aa: heterozygous, A_ phenotype.
- aa: homozygous recessive, aa phenotype.
When you're given information about the amount of individuals of A_ and aa phenotypes in a population, you have no way of knowing if the individuals with the A_ phenotype are homozygous dominant or heterozygous. However, the individuals with aa phenotype have, without a doubt, homozygous recessive genotype, and you can therefore use that information to calculate the allele frequencies.
The genotypic frequencies in Hardy-Weinberg equilibrium are:
- p²= freq (AA)
- 2pq = freq (Aa)
- q²=freq (aa)
And since p + q = 1, after calculating q you can obtain p.