With the help of one example, explain the phenomena of co-dominance and multiple allelism in the human population.
In the case of co-dominance, two alleles for a trait are equally expressed. Example: ABO blood groups are controlled by the gene I. The gene I have three alleles lA, lB and lO. These alleles determine the type of sugar on the RBC surface. Alleles lA and lB are co-dominant and express the AB blood group. Since there are three different alleles and express themselves on the basis of dominance recessiveness and co-dominance, it is a case of multiple allelism.
