Methods of Determining Allele Frequencies from Data on Genotypes
A survey of 100 French individuals from Brittany gave these genotypes. Allele frequencies can be calculated by
  1. Counting Alleles: just add the alleles. For example, frequency of the CCR5l (1) allele is (158+20)/200 = 178/200 = 0.89.

  2. From Genotype Frequencies: add the homozygotes and half the heterozygotes. For example, frequency of the CCR5l (1) allele is 0.79 + (0.5)0.20 = 0.89.