For which two reasons, the operon model is likely to be revised?

Explanation

### Step-by-Step Text Solution

1. **Understanding the Operon Model**:
- The operon model is a genetic regulatory system found in bacteria, where a cluster of genes is controlled by a single promoter. This allows for the coordinated expression of genes that are involved in a related function.

2. **Examples of Operons**:
- Two well-known operons are the **Lac operon** (involved in lactose metabolism) and the **Trp operon** (involved in tryptophan synthesis). These operons illustrate how bacteria can efficiently regulate gene expression in response to environmental changes.

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