Lac operan exerts negative control when
(1). Repressor binds promoter gene.
(2) Repressor binds operator gene.
(3). Inducer binds repressor.
(4) Repressor binds with structural gene.

Explanation

To answer the question about when the Lac operon exerts negative control, let's break down the options step by step:

### Step-by-Step Solution:

1. **Understanding the Lac Operon**: The Lac operon is a set of genes responsible for the metabolism of lactose in bacteria, particularly E. coli. It consists of structural genes (Z, Y, A) and regulatory elements.

2. **Identifying Key Components**:
- **Repressor**: A protein that can bind to the operator region of the operon to inhibit transcription.
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