Question

Which individuals in a population are the most important in determining the numbers for the Hardy-Weinberg principle since one can tell their genotype from their phenotype?

A. homozygous dominant
B. mutated
C. homozygous recessive
D. fittest
E. heterozygous

Answer 1

The answer is C: homozygous recessive

Step-by-step explanation:

Answer 2

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.