A gene whose expression helps to identify transformed cell is known as

Options

A. (a) Selectable marker
B. (b) Vector
C. (c) Plasmid
D. (d) Structural gene

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of a gene that helps identify transformed cells. Transformed cells are those that have taken up foreign DNA, typically through a process like genetic engineering.

2. **Identifying Key Terms**: Key terms in the question include "gene," "expression," and "identify transformed cell." This indicates that we are looking for a specific type of gene that plays a role in the identification process.

3. **Evaluating Options**: The options provided include:
- A) Selectable Marker
- B) Vector
- C) Plasmid
- D) Structural Genes

4. **Analyzing Option A - Selectable Marker**:
- Selectable marker genes are sequences found on plasmids that allow for the identification of cells that have successfully incorporated the plasmid.
- They typically confer resistance to antibiotics, enabling researchers to select for cells that have taken up the plasmid by growing them in the presence of that antibiotic.

5. **Analyzing Option B - Vector**:
- A vector is a vehicle (like a plasmid) used to introduce foreign DNA into a host cell. However, it does not specifically identify transformed cells.

6. **Analyzing Option C - Plasmid**:
- A plasmid is a small circular DNA molecule that can replicate independently of chromosomal DNA. While plasmids can carry selectable markers, they themselves do not identify transformed cells.

7. **Analyzing Option D - Structural Genes**:
- Structural genes encode proteins or enzymes but do not serve the purpose of identifying transformed cells.

8. **Conclusion**: Based on the analysis, the correct answer is A) Selectable Marker, as it specifically refers to genes that allow for the identification of cells that have been transformed.

**Final Answer**: A) Selectable Marker

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