Assertion: A good example of multiple alleles is ABO blood group system.
Reason: When I^A and I^B alleles are present together in ABO blood group system, they both express their own types.

Both Assertion (A) and reason (R) are correct but R is not the correct explanation of A.

The correct answer is Option (2) -Both Assertion (A) and reason (R) are correct, but R is not the correct explanation of A.

Explanation:

Assertion (A): A good example of multiple alleles is the ABO blood group system. This is correct because the ABO system involves three alleles (IA, IB, and i) for a single gene locus, demonstrating multiple alleles.

Reason (R): When IA and IB alleles are present together in the ABO blood group system, they both express their own types. This is also correct. In the ABO blood group system, IA and IB alleles can exhibit codominance when both are present, resulting in the AB blood type, where both A and B antigens are expressed.

While both the assertion and reason are correct, the reason does not provide the correct explanation for the assertion in the context of codominance in the ABO blood group system.