The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.
What provides binding site to RNA polymerase?

Options

A. Exons
B. Promoter
C. Inducer
D. Repressor

Explanation

To answer the question regarding what provides the binding site to RNA polymerase in the lac operon, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Lac Operon Structure**: The lac operon consists of a regulatory gene, three structural genes (lacZ, lacY, and lacA), a promoter, an operator, and a repressor protein. The structural genes are responsible for the metabolism of lactose.

2. **Role of the Inducer**: Lactose acts as an inducer in the lac operon system. When lactose is present, it binds to the repressor protein, causing a conformational change that inactivates the repressor. This prevents the repressor from binding to the operator region.

3. **Function of the Promoter**: The promoter is a specific DNA sequence where RNA polymerase binds to initiate transcription. It is crucial for the transcription of the structural genes in the lac operon.

4. **Access for RNA Polymerase**: When the repressor is inactivated (due to the presence of lactose), RNA polymerase can access the promoter region. This access allows RNA polymerase to begin the transcription of the structural genes.

5. **Conclusion**: The binding site for RNA polymerase in the lac operon is provided by the promoter. The promoter is essential for starting the transcription process.

### Final Answer:
The binding site for RNA polymerase in the lac operon is provided by the **promoter**.

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