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

Options

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

Answer

To answer the question "ABO blood group is determined by gene I which has _____ alleles," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the number of alleles for the gene that determines the ABO blood group.

2. **Identifying the Gene**: The gene responsible for the ABO blood group is known as gene I.

3. **Recognizing Alleles**: Alleles are different forms of a gene. For the ABO blood group, we need to identify how many different alleles exist for gene I.

4. **Multiple Allelism**: The ABO blood group is an example of multiple allelism, which means that there are more than two alleles for a single gene.

5. **Listing the Alleles**: The three alleles for the ABO blood group are:
- Ia (A antigen)
- Ib (B antigen)
- i (O antigen)

6. **Conclusion**: Since there are three different alleles (Ia, Ib, and i) for the gene I, we can conclude that the answer to the question is 3.

### Final Answer:
ABO blood group is determined by gene I which has **3 alleles**.

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