Question

22.two sets of parents Mr.X and Mrs.X Mr.Y and Mrs. Y are claiming the same baby. blood tests give the information that Mr.X and Mrs. X belong to blood group A and Mr.Y belongs to O group and Mrs. Y is of AB blood group. the child belongs to O.explain with reasons to which parent the child belongs?

Answer 1

The alleles A and B are co dominant to each other but are completely dominant to the allele O. (A = B > O)

So, when a O blood group person(with genotype OO) marries a AB blood group person(with genotype AB), it is quite obvious that the progeny would definitely not possess the blood group O. (As, the progeny genotypes might include AO and BO only and not OO)
Hence, the baby does not belong to Mr. and Mrs. Y.

The child's blood group is O and Mr. and Mrs. X belong to the blood group A. If at all, Mr. and Mrs. X's genotypes are as AO and AO, there's every possibility that the baby belongs to Mr. and Mrs. X.