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

Question

Quizplus · Accepted Answer

A person with type O blood must have two copies of the i allele. Therefore, the parents of a person with type O blood must both carry at least one i allele. Choice A cannot be the correct answer because one parent would have to carry an Iᴬ allele, which would result in either type A or AB blood. Choice B cannot be the correct answer because one parent would have to carry an Iᴬ allele, which would result in either type A or AB blood. Choice D cannot be the correct answer because both parents would be either type A or AB blood if they both carried Iᴬᴵᴮ alleles. Therefore, the only possible genotype for the parents of a person with type O blood is Iᴬᶦ and Iᴮᶦ.

A,B,and O Blood Type in Humans Is Controlled by a Single