Question

Mother and father both have blood group A. They have two children one with blood group O and second one with blood group A. Parents have

• A. Mother has homozygotic gene and father is heterozygotic $I^A{I}^A$.
• B. Both are homozygotic $\left(I^A{I}^A\right)$.
• C. Mother is heterozygotic $\left(I^{A}I\right)$ and father is homozygotic $\left(I^A{I}^A\right)$.
• D. Both are heterozygotic $\left(I^{A}I\right)$.

Answer 1

The correct option is D Both are heterozygotic $\left(I^{A}I\right)$.

Blood group A and blood group O is possible if the parents are heterozygous. If both parents have $I^{A}I$, then two cases can be possible for offsprings. Either offspring have A blood group ($I^{A}I$, $I^A{I}^A$) or O blood group ($II$).