Heterozygote
deficiency in sub-populations with differing allele
frequencies:
Wahlund Effect
Two sub-populations of a single
species differ in allele frequency at a locus. In
Sub-population 1, q
= 0.75 and in Sub-population 2, q = 0.25;
in both populations the observed frequency
of heterozygotes is 6 / 16 = 0.375, which is equal
to the expected frequency (2)(0.75)(1 - 0.75)(16) = 0.375.
If the two sub-populations were treated
as a single population, the observed allele
frequencies would be q
=
0.50: the expected
frequency of heterozygotes = (2)(0.50)(1 - 0.50) = 0.500.
The deficiency of
heterozygotes is (Hexp - Hobs) / Hexp
= (0.500 - 0.375) / 0.500 = 0.25.
This deficiency
of heterozygotes from expectation is called the Wahlund Effect, after the
scientist who first observed it in combining genetic data
from two cod populations from different parts of the Baltic
Sea and the waterways leading into it.
Text material
© 2020 by Steven M. Carr