What does the symbol 'P' represent in the Hardy-Weinberg equation?

In the Hardy-Weinberg equation, the symbol 'P' represents the frequency of the dominant allele in a population. This equation is used to understand genetic variation in a population at equilibrium, where allele frequencies remain constant from one generation to the next.

In the equation ( p^2 + 2pq + q^2 = 1 ), ( p ) corresponds to the frequency of the dominant allele, while ( q ) corresponds to the frequency of the recessive allele. The squares and terms in the equation represent the frequencies of the different genotypes: ( p^2 ) for homozygous dominant, ( 2pq ) for heterozygous, and ( q^2 ) for homozygous recessive.

Understanding that 'P' is specifically tied to the dominant allele is critical for predicting genotype frequencies and modeling genetic variation over time. This knowledge is foundational in population genetics and helps in determining how evolutionary forces such as natural selection, genetic drift, and gene flow may affect allele frequencies within a population.