# Hardy-Weinberg equilibrium

###### The **Hardy-Weinberg Law** is an equation that predicts genotypic frequencies based on the frequencies of individual alleles.

The most important message of the Hardy–Weinberg equilibrium is that allele frequencies remain the same from generation to generation unless some agent acts to change them. With that in mind, the Hardy–Weinberg equilibrium allows scientists to determine whether evolutionary agents are operating and their identity (as evidenced by the pattern of deviation from the equilibrium).

The equilibrium also shows the distribution of genotypes that would be expected for a population at genetic equilibrium.

## Five Hardy-Weinberg Assumptions

The five requirements for Hardy-Weinberg are:

- Population size is very large.
- There is no migration between populations.
- There is no mutation.
- Mating is random.
- Natural selection does not affect the alleles under consideration.

## p^{2} + 2pq + q^{2} = 1

###### If the conditions of the Hardy–Weinberg equilibrium are met, then the frequencies of alleles at a locus remain constant from generation to generation, and after one the genotype frequencies will not change after one generation of random mating.

If *p* and *q* represent the frequencies of the dominant and recessive alleles at a locus, then p^{2} and q^{2} are the frequencies of the homozygous genotypes and 2pq (or pq+qp) is the the frequency of the heterozygous genotype. These can be related by the Hardy-Weinberg equation:

**p ^{2} + 2pq + q^{2} = 1**