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

Analyzing the ABO blood group and Rh factor separately:
ABO blood groups:
Mother (A+): Possible genotypes: $I^AI^A$ or $I^Ai$.
Father (B+): Possible genotypes: $I^BI^B$ or $I^Bi$.
Child (A+): Possible genotypes: $I^AI^A$ or $I^Ai$.
Given the child is A+, they must possess at least one $I^A$ allele. As the father is B+, if the child inherits an $I^A$ allele from the mother, they must also inherit an $i$ allele from the father. This implies both parents carry the $i$ allele and are thus heterozygous. Consequently, for the ABO system alone, the genotypes are $I^Ai$ (mother), $I^Bi$ (father), and $I^Ai$ (child).
Rh factor:
Mother (+): Possible genotypes are ++ or +-.
Father (+): Possible genotypes are ++ or +-.
Child (+): Possible genotypes are ++ or +-.
With both parents Rh-positive, their genotypes can be homozygous (++) or heterozygous (+-). The child can inherit a + or – allele from each parent, resulting in a ++ or +- genotype.
Therefore, with an A+ child and positive parents, the sole viable genotype combination from the provided choices yielding an A+ child is: $I^Ai$ | $I^Bi$ | $I^Ai$, corresponding to options B and E.