Question

A woman with blood group ‘O’ marries a man with blood group ‘AB’. The blood group of their son would be:

Options

• ‘A’

• ‘B’

• ‘A’ or ‘B’

• ‘O’

Answer 1

‘A’ or ‘B’

Explanation:

A woman with blood group ‘O’ has the genotype ii (two recessive ‘i’ alleles). A man with blood group ‘AB’ has the genotype I^A I^B, where both alleles are codominant. Their child will inherit one ‘i’ allele from the mother and either an I^A or I^B allele from the father. Therefore, the possible genotypes of the child are I^A i (blood group A) or I^B i (blood group B). The child cannot have blood group O or AB because the child must inherit an ‘i’ allele from the mother (ruling out AB) and cannot inherit an ‘i’ from the father since he has none (ruling out O). Thus, the blood group of the son will be either A or B.