Question

If the blood group of father is 'A' and that of mother is 'B', the blood group of their child could be

• A. A or B or AB
• B. AB only
• C. A or B or AB or O
• D. A or B only

Answer 1

Answer: (C)

A or B or AB or O

A parent with A blood group can have two possible genotypes, “I${}^A$ I${}^A$” and “I${}^A$ I${}^O$”; similarly parent with B blood group can have two possible genotypes, “I${}^B$ I${}^B$” and “I${}^B$ I${}^O$”. Thus, they have three alleles, “I${}^A$”, “I${}^B$” and “I${}^O$” which can make total six genotypes : I${}^A$ I${}^A$, I${}^A$ I${}^O$, I${}^B$ I${}^B$, I${}^B$ I${}^O$ , I${}^A$ I${}^B$ and I${}^O$I${}^O$. Since, I${}^A$ and I${}^B$ alleles are dominant over I${}^O$ allele; the genotypes I${}^A$ I${}^O$ and I${}^B$ I${}^O$ gives A and B blood group respectively. Genotypes I${}^A$ I${}^A$, I${}^B$ I${}^B$, I${}^O$ I${}^O$ show A, B and O blood groups respectively. Due to codominance of "I${}^A$" and "I${}^B$” alleles, the genotype "I${}^A$I${}^B$" produce “AB” blood group respectively. Thus, the six genotypes give total four phenotypes. Hence, parents with A and B blood group can have child with A, B, AB and O blood groups. Correct option is "C".