Question

Mother and father of a person with “$O$” blood group have “$A$” and “$B$” blood group respectively. What would be the genotype of both mother and father?

• A. Mother is homozygous “A” group and father heterozygous for “B”.
• B. Mother is heteroozygous “A” group and father homozygous for “B”.
• C. Both mother and father are heterozygous for “A” and “B” group respectively.
• D. Both mother and father are homozygous for “A” and “B” group respectively.

Answer 1

Answer: (C)

$ABO$ blood group in humans is an example for multiple allelism. The genotype of the person with" $O ^{\prime \prime}$ blood group is $I ^{ O } I ^{ O }$ or ii. Since the mother and father possess $A$ and $B$ blood groups respectively, their genotypes should be heterozygous. $I^{A}$ and $I^{B}$ are dominant genes responsible for $A$ and $B$ blood group respectively. Hence the genotype of mother with" $A^{\prime \prime}$ blood group is $I^{A} I^{O}$ or $A^{A} i$ and the genotype of father is $I ^{ B } I ^{ O }$ or $I^{B} i$.