Person having genotype `I^(A) I^(B)` would show the blood group as AB. Thus is because of

Options

A. pleitropy
B. codominance
C. segregation
D. incomplete dominance

Explanation

To answer the question regarding why a person with the genotype \( I^{A} I^{B} \) shows the blood group AB, we can break down the reasoning step by step.

### Step-by-Step Solution:

1. **Understanding the Genotype**: The genotype \( I^{A} I^{B} \) consists of two alleles: \( I^{A} \) (which codes for the A antigen) and \( I^{B} \) (which codes for the B antigen).

2. **Allele Expression**: In the case of blood groups, both the A and B alleles are co-dominant. This means that when both alleles are present, they are both expressed in the phenotype.

3. **Phenotype Determination**: Since the person has one allele for A and one for B, both antigens are produced on the surface of the red blood cells. This results in the blood group being AB, as both A and B antigens are present.

4. **Co-Dominance Explanation**: The phenomenon that explains this situation is co-dominance, not incomplete dominance. In co-dominance, both alleles contribute equally to the phenotype, resulting in a distinct expression of both traits.

5. **Conclusion**: Therefore, the presence of both \( I^{A} \) and \( I^{B} \) alleles leads to the expression of both A and B antigens, resulting in the blood group AB.

### Final Answer:
The person having genotype \( I^{A} I^{B} \) shows the blood group as AB due to the phenomenon of **co-dominance**.

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