Question

Assertion :A woman is capable of sueing a man for refusing to own this child, he has blood group B and women has A while child has O. Reason: Genetically she is right, he can be father of the child.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

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 ${}^O$ is recessive to both I${}^A$ and I${}^B$. This gives total six genotypes and four phenotypes - A (I${}^A$ I${}^A$ and I${}^A$ I${}^O$), B (I${}^B$ I${}^B$ and I${}^B$ I${}^O$), AB (I${}^A$ I${}^B$) and O (I${}^O$ I${}^O$). Genotype of a child with O blood group will be (I${}^O$ I${}^O$). Thus, parents with A and B blood group should carry atleast one I${}^O$ allele so that the child can have "O" blood group.
Parent generation : I${}^A$ I${}^O$ (mother) x I${}^B$ I${}^O$ (father)

Gametes : I${}^A$ I${}^O$ --> I${}^B$ I${}^O$	I${}^A$	I${}^O$
I${}^B$	I${}^A$ I${}^B$	I${}^B$ I${}^O$
I${}^O$	I${}^A$ I${}^O$	I${}^O$ I${}^O$

F${}_1$ generation phenotypic ratio = 1 A group: 1 AB group: 1 B group : 1 O group; hence, a mother with A blood group and father with B blood group can have a child with O blood group provided that both the parents are heterozygous. Correct option is "A".