Identify the INCORRECT statement from the following with reference to lac operon.

Options

A. (a) It is a unit of gene expression and regulation for lactose sugar metabolism in E. coli.
B. (b) Lactose sugar enters the cell due to the activity of enzyme permease.
C. (c) Operators are present between promoters and structural genes.
D. (d) The structural gene 'Z' code for `beta` - galactosidase, 'Y' for transacetylase, and 'A' for permease.

Answer

To identify the INCORRECT statement regarding the lac operon, let's analyze each option step by step:

1. **Understanding the lac operon**: The lac operon is a group of genes in E. coli that are involved in the metabolism of lactose. It consists of structural genes (lacZ, lacY, and lacA), a promoter, and an operator. The operon allows the bacteria to efficiently utilize lactose when it is available.

2. **Analyzing the options**:
- **Option A**: "It is a unit of gene expression and regulation for lactose sugar metabolism in E. coli."
- This statement is correct. The lac operon is indeed responsible for the regulation of lactose metabolism in E. coli.

- **Option B**: "Lactose sugar enters the cell due to the activity of enzyme permease."
- This statement is also correct. The lacY gene codes for the enzyme permease, which facilitates the entry of lactose into the bacterial cell.

- **Option C**: "Operators are present between promoters and structural genes."
- This statement is correct as well. The operator is located between the promoter and the structural genes in the lac operon, and it plays a crucial role in regulating gene expression.

- **Option D**: "The structural gene Z codes for beta-galactosidase, Y codes for transacetylase, and A for permease."
- This statement is incorrect. The lacZ gene does code for beta-galactosidase, but lacY codes for permease, and lacA codes for transacetylase. The statement incorrectly assigns the functions of the genes.

3. **Conclusion**: Based on the analysis, the incorrect statement is **Option D**.

### Final Answer:
The incorrect statement regarding the lac operon is **Option D**.