m RNA which translates the permease protein is transcribed by which structural gene

Options

A. 1)Z
B. 2)A
C. 3)Y
D. 4)C

Answer

To determine which structural gene transcribes the mRNA that translates the permease protein, we need to analyze the components of the lac operon.

### Step-by-Step Solution:

1. **Understand the lac operon**: The lac operon is a set of genes in E. coli that are responsible for the metabolism of lactose. It consists of three structural genes: lacZ, lacY, and lacA.

2. **Identify the function of each gene**:
- **lacZ**: This gene codes for the enzyme beta-galactosidase, which breaks down lactose into glucose and galactose.
- **lacY**: This gene codes for the enzyme lactose permease, which facilitates the transport of lactose into the bacterial cell.
- **lacA**: This gene codes for the enzyme thiogalactoside transacetylase, which has a different function related to the metabolism of lactose.

3. **Determine the mRNA's role**: The question specifically asks for the mRNA that translates the permease protein. Since permease is coded by the lacY gene, we need to identify which structural gene corresponds to this.

4. **Analyze the options**:
- **Option A (lacZ)**: Incorrect, as it codes for beta-galactosidase.
- **Option B (lacA)**: Incorrect, as it codes for thiogalactoside transacetylase.
- **Option C (lacY)**: Correct, as it codes for lactose permease.
- **Option D (lacC)**: Incorrect, as it is not part of the lac operon.

5. **Conclusion**: The mRNA that translates the permease protein is transcribed by the lacY structural gene.

### Final Answer:
The mRNA which translates the permease protein is transcribed by the **lacY** structural gene.

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