Question

Keerthi and Sadhana delivered babies at the same time in the same nursing home. The babies somehow get exchanged, and confusion ensues. The male baby has blood group O and the female baby has blood group AB. If Keerthi’s blood group is B and Sadhana’s blood group is AB, who is the mother of the male baby?

• A. Keerthi
• B. Sadhana
• C. Data insufficient
• D. None

Answer 1

The correct option is A

Keerthi

Sadhana’s blood group is AB, which means she has the alelles $I^A$ and $I^B$ . For blood group O, both the alleles have present would have to be recessive (ii). So, having passed on either $I^A$ or $I^B$ to her offspring, she cannot deliver a child with blood group O, regardless of what her husband's blood group has been. Keerthi’s blood group on the other hand is B, which could be genotype $\left(I^B{I}^B\right)$ or $\left(I^{B}i\right)$. If she has the genotype $\left(I^{B}i\right)$ she could deliver a baby with blood group O, provided her husband’s also has a blood group with a recessive allele, that is either $\left(I^{A}i\right)$ or $\left(I^{B}i\right)$.
Since it is impossible for Sadhana to have a baby with blood group O, and there is a possibility for Keerthi to have a baby with blood group O, the male baby with blood group O belongs to Keerthi.