Which of the following is required as inducer(s) for the expression of Lac operon ?

Options

A. Galactose
B. Lactose permese and transacetylase
C. Lactose and galactsoe
D. Glucose

Answer

### Step-by-Step Solution:

1. **Understanding the Lac Operon**: The lac operon is a genetic regulatory system found in E. coli and other bacteria. It consists of a cluster of genes that are responsible for the metabolism of lactose. The operon includes a promoter, an operator, and three structural genes (Z, Y, and A).

2. **Role of the Repressor**: The lac operon is normally off because a repressor protein binds to the operator region, preventing transcription of the structural genes. This repressor is produced by a regulatory gene located nearby.

3. **Inducer Function**: An inducer is a molecule that initiates gene expression. In the case of the lac operon, the inducer is lactose. When lactose is present in the environment, it binds to the repressor protein.

4. **Binding of Lactose**: When lactose binds to the repressor, it causes a conformational change in the repressor protein, preventing it from binding to the operator. This allows RNA polymerase to access the promoter and initiate transcription of the structural genes.

5. **Transcription and Translation**: Once transcription occurs, mRNA is produced, which is then translated into proteins that help in the metabolism of lactose. The proteins encoded by the lac operon include beta-galactosidase (Z), permease (Y), and transacetylase (A).

6. **Conclusion**: The question asks for the inducer required for the expression of the lac operon. The correct answer is lactose, as it is the molecule that induces the expression by binding to the repressor.

### Final Answer:
**Lactose** is required as the inducer for the expression of the lac operon.

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