Question

A man with blood group ‘A’ marries a woman with blood group ‘B’. What are all the possible blood groups of their offsprings?
(A) A, B, AB, and O
(B) O only
(C) A and B only
(D) A, B, and AB only

Answer 1

The blood group is the complete blood group system that comprises red blood cell antigens. These antigens are controlled by a series of genes linked closely and are present on the same chromosome. Blood types can be known by a cross between the parents that determine their blood group antigens.

Complete answer: Blood is a fluid connective tissue that is important for the transport of oxygen and other essential molecules throughout the body. The composition of blood includes erythrocytes or red blood cells, leukocytes, and platelets. These components remain the same in all humans. The difference is in the antigen present on the red blood cells. The ABO blood group discovered by Karl Landsteiner explained these antigens. The ABO blood group system consists of four types of blood groups called A, B, AB, and O. These blood types are based on the types of antigens and antibodies present on the red blood cells and in the plasma of blood.
The man has blood group A this means that the antigen on his red blood cells is A and the antibody is B. This will be encoded by a gene ${{I}^{A}}$. On the other hand, the woman will have antigen B and antibody A. This indicates her blood type being B. This will be encoded by a gene ${{I}^{B}}~$. Now, from this, we can conclude that both of the parents have both antigens A and B.
Thus, their offsprings can have A, B, AB, and O blood types, Hence option (A) is correct.
This can be understood by the cross given below.

Note: All of the four blood types are controlled by three alleles that are ${{I}^{A}}$, ${{I}^{B}}~$, and i. Thus, blood groups show the phenomena of multiple allelism. IA and IB are dominant alleles and i is the recessive allele. When the dominant alleles come together they show the effect of co-dominance. This results in the AB blood group.