Question

Children of a father with 'O' blood group and mother of 'AB' blood group have blood group

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

Answer 1

Answer: (D)

Human blood group inheritance is the example of codominance and multiple alleles. It is governed by three alleles namely I${}^A$, I${}^B$ and I${}^O$. I${}^A$ and I${}^B$ show codominance while allele "I${}^O$" is recessive to both "I${}^A$" and "I${}^B$". Thus, the genotype of the parent with “O” blood group is “I${}^O$I${}^O$” ; and that of the parent with “AB” blood group is “I${}^A$I${}^B$”.

Parent generation : I${}^A$I${}^B$ x I${}^O$I${}^O$

Gametes : I${}^A$I${}^B$ ---> I${}^O$I${}^O$	I${}^A$	I${}^B$
I${}^O$	I${}^A$I${}^O$ (blood group A)	I${}^B$I${}^O$ (blood group B)

Thus, their children can have A or B blood groups. Since, the parent with AB blood group does not have I${}^O$ allele; they can't have the child with O blood group (I${}^O$I${}^O$); options A and C are wrong. The parent with O blood group does not have I${}^A$ or I${}^B$ allele; they can't have the child with AB blood group (I${}^A$I${}^B$); options B and C are wrong.