Hardy-Weinberg equilibrium.
<P>
   Under  Hardy-Weinberg  equilibrium,  allele  and  genotype frequencies
   remain constant over generations.
<P>
<BR><LI> The allele frequencies are described by<LI> p + q = 1,
where  p  is  the dominant allele frequency and q is the recessive
allele frequency.
<BR><LI> The genotype frequencies are described by<LI> p^2 + 2pq + q^2 = 1,
where  p^2  and q^2 are frequencies of the homozygous genotype and
2pq is the frequency of the heterozygous genotype.