Inducer molecule in lac-operon of E coli is chemically

Options

A. Disaccharide
B. Amino acids
C. Protein
D. RNA

Answer

### Step-by-Step Solution:

1. **Understanding the Lac Operon**: The lac operon is a set of genes in E. coli that is responsible for the metabolism of lactose. It includes structural genes (Z, Y, and A) that code for enzymes necessary for lactose breakdown.

2. **Identifying the Inducer**: The inducer molecule is a substance that initiates the expression of the operon. In the case of the lac operon, this inducer is lactose.

3. **Chemical Nature of Lactose**: Lactose is a disaccharide, which means it is composed of two monosaccharide units. Specifically, lactose is made up of one molecule of glucose and one molecule of galactose.

4. **Function of the Inducer**: When lactose is present, it binds to the repressor protein produced by the I gene. This binding inactivates the repressor, allowing RNA polymerase to transcribe the structural genes (Z, Y, A), leading to the production of enzymes that break down lactose.

5. **Conclusion**: Therefore, the inducer molecule in the lac operon of E. coli is chemically a disaccharide, specifically lactose.

### Final Answer:
The inducer molecule in the lac operon of E. coli is chemically a disaccharide (lactose).