What percentage chance is there for a couple to have a child with a codominant blood type phenotype?

The question focuses on the inheritance of codominant blood type phenotypes, specifically the ABO blood group system, where alleles A and B are codominant and O is recessive. The combination of these alleles can result in different blood type phenotypes, namely A, B, AB, and O.

To determine the percentage chance for a couple to have a child with a codominant blood type phenotype, we can consider a couple where one parent has type A blood (genotype could be AA or AO) and the other has type B blood (genotype could be BB or BO). The offspring's possible genotypes would then include AA, AO, BB, or BO.

1. If one parent is AA and the other is BB, all offspring will be AB, representing a codominant phenotype. This scenario would yield a 100% chance; however, it's important to also consider combinations involving AO and BO genotypes.

2. If one parent is AO and the other is BO, the potential offspring can have genotypes of AO (type A), BO (type B), AB (type AB, a codominant trait), or OO (type O). Out of these four possibilities, two lead to codomin