A, B, and O blood type in humans is controlled by a single gene with three alleles: I^A, I^B, and i. Type O is the recessive trait. The i allele is recessive to both I^A and I^B. Which of the following could be possible genotypes of the parents of a person with type O blood?

Question

Quizplus · Accepted Answer

In order for a person to have type O blood, they must have two recessive i alleles. This means that both parents must have at least one copy of the i allele. Choice A cannot be correct because IS1U1P1AIBS1S1P0 is a dominant allele and would result in the offspring having either the A or B blood type. Choice B cannot be correct because one parent has the dominant IS1U1P1A allele and would result in the offspring having either the A or AB blood type. Choice D cannot be correct because both parents have a dominant allele, which means the offspring would not have the recessive i allele needed for type O blood. Choice C is correct because both parents have one copy of the recessive i allele, allowing for the possibility of their offspring inheriting two copies and having type O blood.

A, B, and O Blood Type in Humans Is Controlled