Question

A person with blood group A possesses

• A. Antigen A and antibody B
• B. Antigen B and antibody A
• C. No antigen and no antibody
• D. No antigen and A and B antibodies

Answer 1

The correct option is A Antigen A and antibody B

Antigens are foreign substances that induce the immune system to produce antibodies. The 'I${}^A$' and 'I${}^B$' alleles are responsible for the production of the A and B antigens that are present on the surface of the erythrocytes. The antibodies are present in human blood without prior exposure to the antigen which means that people with a particular ABO antigen carry the antibody against the other antigen in their serum. A person with 'A' blood group carries 'A' antigen on their RBCs and anti- B antibodies in their serum. A person with 'B' blood group carries 'B' antigen on their RBCs and anti- A antibodies in their serum. Since, type O persons do not have either antigen on their RBCs, hence they carry both antibodies in their serum. A person with 'AB' blood group carries 'A and B' antigens on their RBCs and no antibodies in their serum; none of the blood group lack both antigen and antibodies.