What does the structural gene (y) of a lac operon code for ?

Options

A. `beta`-galactosidase
B. Transacetylase
C. Permease
D. Glucagon

Answer

To answer the question "What does the structural gene (y) of a lac operon code for?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Lac Operon Structure**: The lac operon is a genetic regulatory system found in E. coli and other bacteria. It consists of three structural genes: lacZ, lacY, and lacA.

2. **Identify the Genes**:
- **lacZ**: This gene codes for the enzyme beta-galactosidase, which is responsible for breaking down lactose into glucose and galactose.
- **lacY**: This is the gene in question.
- **lacA**: This gene codes for the enzyme transacetylase.

3. **Focus on lacY**: The lacY gene specifically codes for a protein known as permease.

4. **Function of Permease**: Permease is a membrane protein that facilitates the transport of lactose into the bacterial cell, allowing the bacteria to utilize lactose as a source of energy.

5. **Conclusion**: Therefore, the structural gene (y) of the lac operon codes for permease.

### Final Answer:
The structural gene (y) of a lac operon codes for permease.

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