Final answer:
Allele frequency indicates the proportion of a specific allele within a population's gene pool, crucial for understanding population evolution. It can change due to natural selection, genetic drift, or the founder effect, against a backdrop of stable frequencies in Hardy-Weinberg equilibrium.
Step-by-step explanation:
The allele frequency, also known as gene frequency, in a population is defined as the proportion of a specific allele among all the alleles of a particular gene within that population. In the field of population genetics, this concept is crucial as it provides the basis for understanding how a population evolves over time.
For instance, if we take the ABO blood type system as an example, the allele frequency of IA can be calculated by dividing the number of IA alleles by the total number of ABO gene copies in the population. Various factors, such as natural selection, genetic drift, and the founder effect, can influence changes in these frequencies, leading to evolution or, in specific conditions characterized by the Hardy-Weinberg equilibrium, to a stable, non-evolving population state.