dear experts

why is blood grouping in humans a case of codominance ?please answe fast experts.............

Codominance is the phenomenon when a gene has more than one dominant allele. So, when two dominant alleles are present in an individual, both of them are expressed co-dominantly. In the case of ABO system of human blood, both A and B alleles are co-dominant. So, when both these alleles are present in a person, the person's blood group is AB.