Question

The sequence of the structural genes in the lac operon is in the order of:

• A. lacZ-lacA-lacY
• B. lacZ-lacY-lacA
• C. lacA-lacY-lacZ
• D. lacA-lacZ-lacY

Hint:

The lac operon is organized as lacZ-lacY-lacA in E. coli, enabling lactose metabolism.

Answer 1

The Correct Option is B

Step 1: Understanding the lac Operon 
The lac operon in Escherichia coli consists of three structural genes involved in lactose metabolism: lacZ (β-galactosidase), lacY (lactose permease), and lacA (thiogalactoside transacetylase). 
Step 2: Evaluating the Options 
- Option (A): Incorrect, the sequence is wrong. 
- Option (B): Correct, lacZ-lacY-lacA is the correct sequence of genes in the operon. 
- Option (C): Incorrect, this sequence does not represent the lac operon gene order. 
- Option (D): Incorrect, this sequence is not correct for the lac operon. 
Step 3: Conclusion 
The correct sequence of the structural genes in the lac operon is lacZ-lacY-lacA.