In an E. coli culture lactose is used as food instead of glucose. If so, answer the following questions:
(1) How do the bacteria respond to the above situation at genetic level?
(2) If lactose is removed from the medium what will happen?

Explanation

### Step-by-Step Text Solution

**(1) How do the bacteria respond to the above situation at the genetic level?**

When E. coli is provided with lactose as a food source instead of glucose, it activates the lac operon, which is a set of genes responsible for the metabolism of lactose. Here’s how the process works:

1. **Lac Operon Structure**: The lac operon consists of three structural genes: lacZ, lacY, and lacA. These genes code for proteins that help in the utilization of lactose.
- **lacZ**: Codes for beta-galactosidase, which breaks down lactose into glucose and galactose.
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