The sequence of structural genes in lac operon is

Options

A. Lac A, Lac Y, Lac Z
B. Lac A , Lac Z, Lac Y
C. Lac Y, Lac Z, Lac A
D. Lac Z , Lac Y, Lac A

Answer

To answer the question about the sequence of structural genes in the lac operon, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding the Lac Operon**: The lac operon is a set of genes responsible for the metabolism of lactose in bacteria, primarily E. coli. It consists of regulatory elements and structural genes.

2. **Identifying the Components**: The lac operon includes:
- **Regulator Gene**: This gene produces a repressor protein that controls the operon.
- **Promoter (P)**: This is the site where RNA polymerase binds to initiate transcription.
- **Operator (O)**: This is the region where the repressor binds to prevent transcription.
- **Structural Genes**: These are the genes that encode proteins necessary for lactose metabolism.

3. **Listing the Structural Genes**: The structural genes in the lac operon are:
- **lacZ**: This gene encodes the enzyme β-galactosidase, which breaks down lactose into glucose and galactose.
- **lacY**: This gene encodes lactose permease, which facilitates the transport of lactose into the cell.
- **lacA**: This gene encodes thiogalactoside transacetylase, which is involved in the detoxification of certain compounds.

4. **Sequence of Structural Genes**: The sequence of the structural genes in the lac operon is:
- **lacZ** → **lacY** → **lacA**

5. **Conclusion**: Therefore, the sequence of structural genes in the lac operon is lacZ, lacY, and lacA.

### Final Answer:
The sequence of structural genes in the lac operon is **lacZ, lacY, lacA**.

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