Question

A woman has $O$ blood group. She has two brothers; one with $A$ group and the other with $B$ group. The genotypes of her parents are

• A. $I^\circ I^\circ -I^{A}I^\circ $
• B. $I^{A}I^\circ -I^{B}I^\circ $
• C. $I^{A}I^{B}-I^\circ I^\circ $
• D. $I^{A}I^\circ -I^{A}I^{B}$

Answer 1

Answer: (B)

A woman with blood group O should have genotype i i i.e. Both of her parents should at least have one i allele. So for having a child with blood group B, there should be at least one parent having a copy of IB allele. Parents with Iai and Ibi will have children with Iai (A blood group), Ibi (B blood group), IaIb (AB blood group) and ii (O blood group).