Which of the following blood group is considered example of co-dominance ?

Options

A. A
B. B
C. AB
D. O

Answer

**Step-by-Step Solution:**

1. **Understanding Blood Groups**: Blood groups in humans are determined by specific antigens present on the surface of red blood cells (RBCs). The ABO blood group system is based on the presence or absence of these antigens.

2. **Identifying Alleles**: There are three alleles that determine the ABO blood group:
- **IA**: Produces A antigen.
- **IB**: Produces B antigen.
- **i**: Produces no antigen (O blood group).

3. **Explaining Co-dominance**: Co-dominance occurs when two different alleles are expressed equally in the phenotype. In the case of blood groups, both IA and IB alleles are co-dominant.

4. **Genotypes and Phenotypes**:
- **AA (IAIA)** or **AO (IAi)** results in blood group A.
- **BB (IBIB)** or **BO (IBi)** results in blood group B.
- **OO (ii)** results in blood group O.
- **AB (IAIB)** results in blood group AB, where both A and B antigens are present on the RBC surface.

5. **Conclusion**: The blood group that exemplifies co-dominance is **AB**. This is because both IA and IB alleles are expressed equally, resulting in the presence of both A and B antigens.

**Final Answer**: The blood group that is considered an example of co-dominance is **AB**.

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