Codominant inheritance:
Codominant means both alleles of a heterozygous gene pair both have full phenotypic expression. The dividing line between intermediate inheritance and co-dominant inheritance is fuzzy. Codominance is more likely to be used when biochemistry is concerned, as in blood types. Codominance means that both alleles at a locus are expressed. Codomininance in X-linked genes is a special case that will be treated under sex-linked inheritance. An example of codominance is sickle-cell anaemia. Individuals who are homozygous for normal allele have normal haemoglobin in their blood cells. The homozygous for the sickle-cell allele have abnormal haemoglobin, this means there blood cells are awkwardly shaped and the red blood cells lack the sufficiency to carry the amount of oxygen required. Heterozygous patients have red blood cells which are reasonably normal unless there is a low concentration of oxygen. The heterozygotes suffer little effects but they have an advantage of being resistant to infection by the malarial parasite.