Question

A baby of blood group A cannot belong to parents of blood group

• A. Husband O, wife AB
• B. Husband A, wife B
• C. Husband B, wife O
• D. Husband AB, wife A

Answer 1

The correct option is C Husband B, wife O

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. I${}^A$ and I${}^B$ show codominance while allele "i" is recessive to both "I${}^A$" and "I${}^B$". Possible genotypes of a child with “A” blood group are “I${}^A$ I${}^A$” or I${}^A$i. This means that either both parents should have at least one copy of “I${}^A$” allele or one parent should have one copy of “I${}^A$” and another parent should have at least one copy of “i” allele. Husband with O (ii) and wife with AB “I${}^A$ I${}^B$” blood group have one “i” allele in husband and one “I${}^A$” allele in the wife; thus they can have a child with A blood group. Option A is incorrect. Husband with A; “I${}^A$ I${}^A$ or I${}^A$ i” and wife with B; “I${}^B$ i” blood group have “I${}^A$” allele in husband and one “i” allele in wife; thus they can have a child with A blood group. Option B is incorrect. Husband with B “I${}^B$i” and wife with O “ii” blood group have one “i” allele in husband and but “I${}^A$” allele is absent in both parents ; thus they can’t have a child with A blood group. Option C is correct. Husband with AB; “I${}^A$ I${}^B$” and wife with A; “I${}^A$ i” blood group have “I${}^A$” allele in husband and one “i” allele in wife; thus they can have a child with A blood group. Option D is incorrect.