Which statement best describes the difference between gene frequency and genotypic frequency?

Which statement best describes the difference between gene frequency and genotypic frequency?

• A. Genotypic frequency refers to alleles at a locus; gene frequency refers to genotypes
• B. Gene frequency refers to alleles at a locus; genotypic frequency refers to genotypes
• C. Gene frequency is about phenotypes; genotypic frequency is about genes
• D. Genotypic frequency is about individuals' phenotypes

Answer: (B)

Allele (gene) frequency is about how common each allele is in the population’s gene pool, while genotypic frequency is about how common each genotype is among individuals. You’ll often denote allele frequencies as p and q for a two-allele locus, with p + q = 1. Genotypic frequencies describe the proportions of individuals with genotypes like AA, Aa, and aa, and these add up to 1 as well. In a population in Hardy-Weinberg equilibrium, the genotype frequencies are p^2, 2pq, and q^2, directly derived from the allele frequencies. For example, if p = 0.7 and q = 0.3, expected genotype frequencies would be 0.49 for AA, 0.42 for Aa, and 0.09 for aa. So the best description is that gene frequency refers to alleles at a locus, whereas genotypic frequency refers to the genotypes of individuals.

Allele (gene) frequency is about how common each allele is in the population’s gene pool, while genotypic frequency is about how common each genotype is among individuals.

You’ll often denote allele frequencies as p and q for a two-allele locus, with p + q = 1. Genotypic frequencies describe the proportions of individuals with genotypes like AA, Aa, and aa, and these add up to 1 as well. In a population in Hardy-Weinberg equilibrium, the genotype frequencies are p^2, 2pq, and q^2, directly derived from the allele frequencies. For example, if p = 0.7 and q = 0.3, expected genotype frequencies would be 0.49 for AA, 0.42 for Aa, and 0.09 for aa.

So the best description is that gene frequency refers to alleles at a locus, whereas genotypic frequency refers to the genotypes of individuals.