Genes located on same locus but having different expressions are

Options

A. Multiple alleles
B. Oncogenes
C. Polygenes
D. Codominants

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about genes that are located on the same locus but exhibit different expressions. This means we are looking for a specific genetic phenomenon where variations of a gene exist at the same position on homologous chromosomes.

2. **Identifying Key Terms:**
- **Locus:** The specific location of a gene on a chromosome.
- **Different Expressions:** This refers to variations in the phenotype or traits that result from the different alleles present at the same locus.

3. **Analyzing the Options:**
- **Multiple Alleles:** This refers to the presence of more than two alleles for a single gene at a locus. For example, the ABO blood group system has three alleles (I^A, I^B, and i) at the same locus, leading to different blood types.
- **Oncogenes:** These are genes that can lead to cancer when mutated. They do not specifically refer to variations at the same locus.
- **Polygenes:** These are multiple genes that contribute to a single trait, but they are not located at the same locus.
- **Co-dominance:** This is a situation where two alleles at a locus are both expressed, but it does not pertain to the presence of multiple alleles.

4. **Conclusion:**
The correct answer is **multiple alleles**, as they are genes located at the same locus but having different expressions.

5. **Final Answer:**
Genes located on the same locus but having different expressions are called **multiple alleles**.

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