Gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation.
This is known as the Hardy–Weinberg law in honor of the two researchers who first realized the significance of the binomial expansion to population genetics and hence to evolution.
Evolution involves changes in the gene pool. A population in Hardy–Weinberg equilibrium shows no change.

The mutation is any random sudden heritable change occurring in the genetic material. Sexual selection refers to the selection of a mate by an organism.