Question

The mother has A⁺ blood group the father has B⁺ and the child is A⁺. What can be the possibility of genotypes of all three, respectively?
(A) I ^AI ^A | I ^Bi | I^Bi
(B) I ^AI ^A | I ^Bi | I ^Ai
(C) I ^Bi | I ^AI ^A | I ^AI ^B
(D) I ^AI ^A | I ^BI ^B | I ^Ai
(E) I ^Ai | I ^Bi | I ^Ai
Choose the correct answer from the option given below:

• A. C and D
• B. D and A
• C. A and B
• D. B and E

Answer 1

The Correct Option is D

Let's consider the ABO blood group system and the Rh factor separately.
ABO blood groups: 
Mother (A+): Possible genotypes are $I^AI^A$ or $I^Ai$. 
Father (B+): Possible genotypes are $I^BI^B$ or $I^Bi$. 
Child (A+): Possible genotypes are $I^AI^A$ or $I^Ai$.
Since the child is A+, they must have received at least one $I^A$ allele. Since the father is B+, if the child received an $I^A$ allele from the mother, then they must have received an $i$ allele from the father. This means both the mother and father must carry the $i$ allele, so both must be heterozygous. Therefore, for the ABO blood group system alone, the genotypes must be $I^Ai$, $I^Bi$, and $I^Ai$ for mother, father, and child, respectively.
Rh factor:
Mother (+): Possible genotypes are ++ or +-. 
Father (+): Possible genotypes are ++ or +-. 
Child (+): Possible genotypes are ++ or +-.
Since both parents are Rh-positive, they can either be homozygous (+++) or heterozygous (+-). The child can inherit either a + or – allele from each parent, resulting in either ++ or +-.
Therefore, since the child is A+, and both parents are positive, the only possible genotype combination from the provided options that yields an A+ child is: $I^Ai$ | $I^Bi$ | $I^Ai$, which are options B and E.