Co-dominance

Co-dominance can be considered to be non-mendalian inheritance. In co-dominance there is equal expression of two alleles as the phenotype. If the individual is heterozygous both alleles will be expressed equally. An example of this would be the AB blood group. The genotypes for the A and B antigens are codominant with each other and dominant over the recessive antigen O. This means that the red blood cells will present both A antigens and B antigens on its cell surface membrane.

This is different to incomplete dominance, where the phenotype expressed by an individual is a mixture of both parent alleles. This happens as a result of the dominant allele not being completely expressed over its recessive counter part. An example of this would be a red flower and white flower producing a progeny pink flower.