Question

A man of blood group A marries a woman of blood group AB. Which blood type in the offspring would indicate that the man is a heterozygote?

• A. AB
• B. A
• C. O
• D. B

Answer 1

The correct option is D

B

If the father’s blood type is heterozygous A $\left(I^{A}i\right)$ and mother’s blood group is AB $\left(I^A{I}^B\right)$, the blood types of the children are shown below. As you can see children can have the blood group B.

If the father is homozygous for blood group A $\left(I^A{I}^A\right)$. The blood group of the children would be as shown below. As you can see the offspring will not have the blood group B.

Therefore the presence of blood group B in children would indicate that the father is a heterozygote for blood group A.