ABO blood group is determined by gene I which has _____ alleles.

Options

A. 2
B. 4
C. 6
D. 3

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks how many alleles determine the ABO blood group, which is controlled by the gene I.

2. **Identifying the Concept**: The ABO blood group is an example of multiple allelism, where a single gene has more than two alleles.

3. **Identifying the Alleles**: The gene I has three allelic forms:
- I^A (which codes for type A blood)
- I^B (which codes for type B blood)
- i (which is the O blood type)

4. **Conclusion on the Number of Alleles**: Since there are three different alleles (I^A, I^B, and i) for the gene I, we conclude that the ABO blood group is determined by a gene that has three alleles.

5. **Final Answer**: Therefore, the answer to the question is that the ABO blood group is determined by gene I which has **3 alleles**.

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