Question

A baby of blood group A cannot belong to the parents of blood group
A) Husband O, Wife AB
B) Husband A, Wife B
C) Husband B, Wife O
D) Husband AB, Wife A

Answer 1

Blood group is inherited by our parents like we inherit hair colour, eye colour etc. The ABO blood group is regulated by a single gene called the ABO gene. It has multiple alleles and shows codominance.

Complete answer:
Human blood group inheritance is based on multiple alleles and on the principle of codominance. IA, IB, IO are the alleles of the ABO gene. I stand for isoagglutinogen or antigen. The genotypes of the blood group are as follows- A (IA IA, IA IO), B (IB IB, IB IO), AB (IA IB) and O (IO IO). IA and IB are dominant whereas IO is recessive.

According to the question, the baby has blood group A. So the possible genotypes could be (IA IA, IA IO). The parent should have at least one copy of IA.

A) In the first option Husband with blood group O (IO IO, and wife with AB (IA IB), They can have a child which can have blood group A, B, AB.
B) In second option- Husband with A(IA IA, IA IO), wife with B(IB IB, IB IO), They can have A, B, AB
C) In third option- Husband B(IB IB, IB IO), wife O(IO IO). They will have a child of blood group B or O
D) In fourth option- Husband AB (IA IB), wife A (IA IA, IA IO), they can have children with blood group A, B or AB

Thus the correct answer is (C). Husband B, Wife O cannot have a baby with blood group A.

Note: The IA allele gives type A, IB allele give type B and IO allele gives type O. IAand IB are dominant over IO. IA and IB is an example of codominance. The blood group inheritance is used to find out the paternity of the child.