Human blood groups are determined by multiplic gene.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question states that human blood groups are determined by multiple genes. We need to analyze whether this statement is true or false.

2. **Clarifying Terminology:**
- **Multiple Genes:** Refers to a situation where more than one gene controls a particular trait.
- **Multiple Alleles:** Refers to a situation where a single gene has more than two alleles (alternative forms).

3. **Identifying the Correct Concept:**
Human blood groups are determined by multiple alleles, not multiple genes. The ABO blood group system is controlled by a single gene that has three alleles: IA, IB, and IO.

4. **Explaining the Alleles:**
- **IA and IB:** These alleles are dominant over IO.
- **IO:** This allele is recessive.
- The presence of IA and IB leads to the A and B blood types, respectively, while IO leads to the O blood type.

5. **Understanding Blood Group Combinations:**
- **Blood Group A:** Can be IAIA or IAIO.
- **Blood Group B:** Can be IBIB or IBIO.
- **Blood Group AB:** Is IAIB (both alleles are expressed, showing co-dominance).
- **Blood Group O:** Is IOIO (homozygous recessive).

6. **Conclusion:**
The statement that human blood groups are determined by multiple genes is false. Instead, they are determined by multiple alleles of a single gene.

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