CBSE Class 12-science Answered

A cross is carried out between the heterozygous father (for blood group B) and the heterozygous mother (for blood group A) to get four children with different blood groups.

All the four blood groups are controlled by three allelic genes I^A, I^B, i which exhibit an instance of multiple allelism.  Both I^A and I^B are dominant over i. However, when together, both are dominant and show the phenomena of co-dominance, forming the blood group AB. Six genotypes are possible with the combination of these three alleles.