What does allele frequency measure in population genetics?

Allele frequency measures how common an allele is within a population, quantifying its relative prevalence compared to other alleles at the same locus. This metric is crucial in population genetics, as it provides insight into the genetic diversity of a population and can help track changes over time due to factors like natural selection, genetic drift, or gene flow. By assessing allele frequencies, researchers can determine how traits may evolve and understand the genetic structure of populations.

The other choices do not directly pertain to allele frequency. For example, the total number of individuals in a species relates to population size rather than allele prevalence. The genetic makeup of an individual refers to the specific combination of alleles an organism possesses, while the average lifespan of a population is unrelated to genetic composition.