Monohybrid Cross Problem Set

Problem 11: Codominant alleles: The human ABO markers

Human blood type is determined by codominant alleles. There are three different alleles, known as IA, IB, and i. The IA and IB alleles are co-dominant, and the i allele is recessive.

The possible human phenotypes for blood group are type A, type B, type AB, and type O. Type A and B individuals can be either homozygous (IAIA or IBIB, respectively), or heterozygous (IAi or IBi, respectively).

A woman with type A blood and a man with type B blood could potentially have offspring with which of the following blood types?

A. type A

B. type B

C. type AB

D. type O

E. all of the above