Inducer of Lac operon is

Options

A. Repressor protein
B. Lactose
C. RNA polymerase
D. Permease

Answer

**Step-by-Step Solution:**

1. **Understanding the Lac Operon**: The Lac operon is a set of genes in bacteria that are involved in the metabolism of lactose. It consists of structural genes that code for proteins necessary for lactose utilization, a promoter, and an operator.

2. **Identifying the Inducer**: An inducer is a molecule that initiates gene expression. In the case of the Lac operon, the presence of lactose serves as the inducer.

3. **Mechanism of Action**: When lactose is present in the environment, it binds to the repressor protein associated with the Lac operon. This binding changes the shape of the repressor protein, preventing it from attaching to the operator region of the operon.

4. **Result of Inducer Action**: With the repressor protein unable to bind to the operator, RNA polymerase can then access the promoter and transcribe the genes necessary for lactose metabolism. This allows the bacteria to utilize lactose as an energy source.

5. **Conclusion**: Therefore, the inducer of the Lac operon is lactose, as it is the molecule that triggers the expression of the genes involved in lactose metabolism.

**Final Answer**: The inducer of the Lac operon is lactose.

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