Question

A child’s blood group is ‘O’. The parent’s blood groups cannot be

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

Answer 1

The correct option is C

AB and O

The correct option is C.

Explanation of correct option:

1. ABO blood grouping in humans is controlled by the ‘I’ gene, which has three alleles (I^A, I^B, and i).
2. Each individual inherits two alleles from their parents. I^A and I^B show codominance over i.
3. A person’s blood group is classified as ‘O’ if allele i is expressed (homozygous recessive condition).
4. Moreover, when I^A and I^B are present, both alleles are expressed, and the blood group type is AB.
5. If a child’s blood group is ‘O’, both of the parents should have at least one i allele.
6. Therefore, parents having ‘AB’ and ‘O’ blood group cannot have a child with blood group ‘O’.

Final answer: A child’s blood group is ‘O’. The parent’s blood groups cannot be AB and O.