Question

The gene that codes for proteins present on RBCs has three alleles: $I^A$, $I^B$, and i. $I^A$ codes for protein type A, $I^B$ codes for protein type B, and i codes for the absence of protein. $I^A$ and $I^B$ are codominant and i is recessive to both $I^A$ and $I^B$. A woman with blood type A and a man with blood type AB marry and produce children. Which of the following blood types is not possible in their children?

• A. Type A
• B. Type B
• C. Type O
• D. Type AB
• E. All blood types are possible in their children

Answer 1

The correct option is C Type O

The genotype of the woman with type A blood can be either I${}^A$I${}^A$ or I${}^A$i. The genotype of the man with AB blood group is I${}^A$I${}^B$. To have a child with A blood group, both parents should have at least one I${}^A$ allele; the given couple can have type A child. The given couple can have the child with type B blood if the woman is heterozygous (I${}^A$i). To have a child with O blood group, both parents should have at least one i allele; the given couple can not have the child with O blood group. To have a child with AB blood group, one parent should have one I${}^A$ allele and other should have at least one I${}^B$ allele; the given couple can have the child with AB blood group.

Therefore, the correct answer is option C.