The genotype that illustrates codominance of alleles that control blood type in humans is AB.

Here's why:

* Codominance means that both alleles in a heterozygous genotype are expressed equally.

* In the ABO blood group system, there are three alleles: A, B, and O.

* Alleles A and B are codominant. This means that if an individual inherits both the A and B alleles (genotype AB), they will express both A and B antigens on their red blood cells, resulting in blood type AB.

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