LabBench Activity

Allelic Frequency vs. Genotypic Frequency

Allelic Frequency

If you are told that the frequency of a recessive allele in a population is 10%, you are directly given q, since by definition q is the frequency of the recessive allele. This comprises all the copies of the recessive allele that are present in heterozygotes as well as all the copies of the allele in individuals that show the recessive phenotype. What is q for this population?

If you need help, look back at the Hardy-Weinberg equation.

Genotypic Frequency

Genotypic frequency is the frequency of a genotype—homozygous recessive, homozygous dominant, or heterozygous—in a population. If you don't know the frequency of the recessive allele, you can calculate it if you know the frequency of individuals with the recessive phenotype (their genotype must be homozygous recessive).

Sample Problem

If you observe a population and find that 16% show the recessive trait, you know the frequency of the aa genotype. This means you know q2. What is q for this population?