Question

Two parents with blood types A and B have a child who has O blood type. What is the chance that their next child will be A?

1) 0
2) 1/2
3) 1/8
4) 1
5) 1/4

Answer 1

Option 2.

Two heterozygous parents, one with blood type A (AO) and another with blood type B (BO), have a 50% chance (1/2) of having a child with blood type A. The correct option in the final answer is 1/2.

Step-by-step explanation:

The question asks about the inheritance of the ABO blood type system in humans, which is a classic example of codominance and multiple alleles.

If we have two parents, one with blood type A and the other with blood type B, and they have already produced a child with blood type O, this indicates that both parents must be heterozygous (A must be AO and B must be BO).

The possible genotypes for their offspring are 25% AA, 25% AO (which is phenotypically A), 25% BB, 25% BO (which is phenotypically B), and 25% AB.

There is no chance for another O type because O can only occur if both parents provide the 'i' allele.

Therefore, the chance for the next child to be blood type A (either AA or AO) is 25% + 25% = 50% or 1/2.

The correct option in the final answer for the chance that their next child will be A is 1/2.