Question

Possible blood groups of children borne to parents having A and AB groups are

• A. O, A
• B. A, B, AB
• C. O, A, B
• D. O, A, B, AB

Answer 1

Answer: (B)

A, B, AB

Human blood group inheritance is the example of co-dominance and multiple alleles. It is governed by three alleles namely I${}^A$, I${}^B$ and I${}^O$. I${}^A$ and I${}^B$ show co-dominance while allele I${}^O$ is recessive to both I${}^A$ and I${}^B$. Genotype of a person with 'A' blood group can be I${}^A$I${}^O$ or I${}^A$I${}^A$ and that of parent with 'AB' blood group is I${}^A$I${}^B$. The alleles I${}^A$, I${}^O$ and I${}^B$ can make three genotypic combinations, namely I${}^A$I${}^A$ (blood group A), I${}^A$I${}^O$ (blood group A), I${}^A$I${}^B$ (blood group AB) and I${}^B$I${}^O$ (blood group B). Thus, the possible blood group of their children are A, B and AB. To have a child with O blood group, both parent should have at least one I${}^O$ allele; thus they can’t have a child with O blood group.

Thus, the correct answer is option B.