Question

Explain the differences among an allele frequency, a phenotypic frequency, and a genotypic frequency.

Short answer

Allele frequency refers to how often a specific allele appears in a population; phenotypic frequency is the ratio of individuals exhibiting a particular observable characteristic in a population; genotypic frequency refers to the proportion of individuals in a population that carry a particular genotype. The key difference is that allele frequency relates to a form of gene, phenotypic frequency to observable traits, and genotypic frequency to specific combinations of alleles.

Step-by-step solution

Define Allele Frequency

Allele frequency refers to how often a specific allele appears in a population. It is typically measured as a proportion or a percentage. For example, if a gene has two alleles (A and a), and 40% of the alleles in the population are A, then the frequency of the A allele is 0.4 or 40%.

Define Phenotypic Frequency

Phenotypic frequency refers to the ratio of individuals exhibiting a particular observable characteristic or phenotype in a population. Phenotypes can be influenced by multiple genes and environmental factors. For example, if there are 100 individuals in a population and 70 have green eyes (the phenotype), then the phenotypic frequency for green eyes is 0.7 or 70%.

Define Genotypic Frequency

Genotypic frequency refers to the proportion of individuals in a population that carry a particular genotype. A genotype consists of the set of genes in an organism's genome. For example, if there are 100 individuals in a population and 20 of them are homozygous for allele A (AA), then the genotypic frequency for AA is 0.2 or 20%.

Compare the Three Concepts

While all three terms - allele frequency, phenotypic frequency and genotypic frequency - deal with frequency or proportions, they refer to different aspects. Allele frequency deals with the occurrence of a particular form of a gene, the phenotypic frequency deals with observable traits and the genotypic frequency deals with the presence of specific combinations of alleles in an organism.