AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

CODOMINANCE

• If the heterozygote exhibits a mixture of the phenotypic characters of both homozygotes, instead of a single intermediate expression, then both alleles are called co-dominant alleles.
• The phenotypic ratio is 1: 2: 1, identical as that of incomplete or intermediate dominance.

Example

• MN blood group antigens in human : Allele L^M for M-type blood is codominant with allele L^N for N-type blood. The heterozygotes L^ML^N will have both M and N antigens on the red blood cells.
• Hair colour in Short-horn cattle: If we cross a red bull with a white cow, the offspring are reddish gray or roan (mixture of red hairs and white hairs).

 To view "Co-dominance Animation"