Question

$I^A$ allele produces the trait _________________ , while $I^B$ produces _______________ on human RBCs.

• A. antigen A; antigen B
• B. antibody A; antibody B
• C. antibody B; antibody A
• D. antigen A; antigen A

Answer 1

The correct option is A antigen A; antigen B

The alleles mentioned above are two of the three alleles involved in the control of ABO blood groups in humans. The $I^A$ allele produces a glycosyl transferase enzyme that adds the sugar α N-acetyl galactosamine to the polysaccharide to produce the A antigen on the surface of RBCs. The $I^B$ allele produces a different glycosyltransferase enzyme that adds the sugar galactose to produce the B antigen on the surface of RBCs.