How are evolution and allele frequency related

Evolution is a process that causes an acceleration in genetic change within a population. Allele frequency is the measure of frequency of a certain allele within a population. Allele frequency is an indication that evolution is occurring because a change in allele frequency means a change in the genetics of a population. Also, evolutionary change can’t happen without changes in the allele frequency.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.