DragonflyIssuesInEvolution13 Wiki

The incidence of a specific type of gene in a population.  

How to calculate it

The allele frequency is calculated by dividing the number of times the type of gene is observed in a population by the total number of genes for the type you are looking at.  

What is it used for?

The changes in an allele frequency are used as evidence of evolution or genetic change within a population.  It is also a key component of the hardy wienberg model.