Question

If both the parents have AB blood groups, which of the following blood groups their offspring cannot have?

• A. A
• B. B
• C. AB
• D. O

Answer 1

The correct option is D O

The IA allele gives type A, IB gives type B, and IO gives type O. As both IA and IB are dominant over IO, only IO/IO people have type O blood. Individuals with IA/IA or IA/IO have type A blood, and individuals with IB/IB or IB/IO have type B. IA/IB people have both phenotypes, because A and B express a special dominance relationship: codominance, which means that type A and B parents can have an AB child. If both the parents are AB then their genotypes will be IA/IB and this combination cannot give rise to O blood group. Therefore, the correct answer is option D.