The Lac operon "Inducer Lactose" serves as an enzyme substrate for

Options

A. Transacetylase
B. Endonuclease
C. Permease
D. Beta-galactosidase

Answer

To solve the question regarding the Lac operon and the role of the inducer lactose, we can break down the answer into several steps:

### Step-by-Step Solution:

1. **Understanding the Lac Operon**:
- The Lac operon is a genetic regulatory system found in E. coli and other bacteria. It consists of a cluster of genes that are involved in the metabolism of lactose.

2. **Components of the Lac Operon**:
- The Lac operon includes:
- **Regulatory Gene (R)**: Codes for the repressor protein.
- **Promoter**: The site where RNA polymerase binds to initiate transcription.
- **Operator**: The site where the repressor binds to prevent transcription.
- **Structural Genes (Z, Y, A)**:
- **Z gene**: Codes for beta-galactosidase.
- **Y gene**: Codes for permease.
- **A gene**: Codes for transacetylase.

3. **Role of Lactose**:
- Lactose acts as an inducer in the Lac operon. When lactose is present, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator.

4. **Transcription Activation**:
- With the repressor no longer bound to the operator, RNA polymerase can bind to the promoter and initiate transcription of the structural genes (Z, Y, A).

5. **Function of Beta-Galactosidase**:
- The primary role of beta-galactosidase (coded by the Z gene) is to break down lactose into glucose and galactose, making it an enzyme substrate for lactose.

6. **Conclusion**:
- Therefore, the inducer lactose serves as an enzyme substrate specifically for **beta-galactosidase**.

### Final Answer:
The Lac operon "Inducer Lactose" serves as an enzyme substrate for **beta-galactosidase**.

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