Introduction to Population and Evolutionary Genetics

Deriving Gene (or Allelic) Frequencies

To determine the allelic frequencies we simply count the number of M or N alleles and divide by the total number of alleles.

f(M) = [(2 x 1787) + 3039]/12,258 = 0.5395

f(N) = [(2 x 1303) + 3039]/12,258 = 0.4605

By convention one of the alleles is given the designation p and the other q. Also p + q = 1.

p=0.5395 and q=0.4605

Furthermore, a population is considered by population geneticists to be polymorphic if two alleles are segregating and the frequency of the most frequent allele is less than 0.99.