A trait controlled by a gene at several loci is an example of

Options

A. Multiple allelism
B. Incomplete dominance
C. Pleiotropy
D. Polygenic inhertance

Answer

To solve the question "A trait controlled by a gene at several loci is an example of," we need to analyze the options provided and understand the genetic concepts involved.

### Step-by-Step Solution:

1. **Understanding the Question**:
- The question is asking about a trait that is influenced by multiple loci (positions on a chromosome). This means we are looking for a genetic phenomenon where more than one gene influences a single trait.

2. **Analyzing the Options**:
- **Option 1: Multiple Allelism**:
- This refers to a situation where a single gene has more than two alleles. An example is the ABO blood group system. However, this does not involve multiple loci; it involves variations of a single gene.
- **Conclusion**: Incorrect.

- **Option 2: Incomplete Dominance**:
- Incomplete dominance occurs when the phenotype of heterozygotes is intermediate between the phenotypes of the two homozygotes. For example, crossing red and white flowers results in pink flowers. This concept deals with the expression of alleles rather than multiple loci.
- **Conclusion**: Incorrect.

- **Option 3: Pleiotropy**:
- Pleiotropy occurs when one gene influences multiple phenotypic traits. However, this does not refer to multiple loci but rather to a single gene affecting several traits.
- **Conclusion**: Incorrect.

- **Option 4: Polygenic Inheritance**:
- Polygenic inheritance refers to a trait that is controlled by two or more genes (loci). Traits such as skin color, height, and weight are examples where multiple genes contribute to the final phenotype. This matches the description of a trait controlled by a gene at several loci.
- **Conclusion**: Correct.

3. **Final Answer**:
- The correct answer is **Polygenic Inheritance**.