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 codominant, 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

But if the man was type O rather than type B, offspring of type B and type AB would not be possible.

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Thursday, October 1, 1998
Revised: November 2004
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