Which is incorrect

Options

A. i-gene codes for the repressor of lac operon
B. z-gene codes for the beta-galactosidase
C. y-gene codes for transacetylase
D. three gene products are required for metabolism of lactose

Answer

**Step-by-Step Solution:**

1. **Understanding Lac Operon:**
- The Lac Operon is a group of genes found in prokaryotic organisms, particularly in E. coli, that are involved in the metabolism of lactose. It consists of regulatory and structural genes that work together to regulate the breakdown of lactose into glucose and galactose.

2. **Components of Lac Operon:**
- The Lac Operon consists of:
- **Regulatory Gene (I gene):** Codes for the repressor protein that inhibits the operon when lactose is not present.
- **Structural Genes:**
- **Z gene:** Codes for beta-galactosidase, an enzyme that breaks down lactose.
- **Y gene:** Codes for permease, which facilitates the entry of lactose into the cell.
- **A gene:** Codes for transacetylase, which is involved in the metabolism of lactose.

3. **Analyzing the Statements:**
- Now, we will evaluate the statements provided in the question:
- **Statement 1:** "I gene codes for repressor of Lac operon."
- This statement is correct.
- **Statement 2:** "Z gene codes for beta-galactosidase."
- This statement is also correct.
- **Statement 3:** "Y-gene codes for transacetylase."
- This statement is incorrect. The Y gene codes for permease, while the A gene codes for transacetylase.
- **Statement 4:** "All three gene products are required for lactose metabolism."
- This statement is correct as all three gene products (beta-galactosidase, permease, and transacetylase) contribute to the metabolism of lactose.

4. **Conclusion:**
- The incorrect statement among the four provided is **Statement 3**, which claims that the Y gene codes for transacetylase.

**Final Answer:**
- The incorrect statement is: "Y-gene codes for transacetylase."

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