Under Hardy-Weinberg equilibrium, the
   frequencies  of  all  three  genotypes  can  be  calculated  once  the
   frequency of either allele is known.

   Heterozygotes  increase rapidly in a population as the values of p and
   q move from 0 or 1.

   Most genetic diseases are recessive traits with low frequencies in the
   population,   and   most   individuals   carrying   the   allele   are
   heterozygotes.