Hardy-Weinberg Equilibrium (HWE)

Hardy-Weinberg equilibrium describes the relationship between the gametic or allele frequencies, and the resulting genotypic frequencies. It holds if the following properties are true for the given locus,

1. Random mating or panmixia: the choice of a mate is not influenced by his/her genotype at the locus.
2. The locus does not affect the chance of mating at all, either by altering fertility or decreasing survival to reproductive age.

If these properties hold, then the probability that two gametes will meet and give rise to a new genotype is simply the product of the allele frequencies (a la binomial):

Pr(MM)= Pr(M) x Pr(M)

Pr(NN)= Pr(N) x Pr(N)

Pr(MN)= 1 - Pr(MM) - Pr(NN) = 2 x Pr(M) x Pr(N).