Question

Wild type E.coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as the sugar. Which one of the following changes take place?

• A. The lac operon is repressed.
• B. All operons are induced.
• C. E. coli cells stop dividing.
• D. The lac operon is induced.

Answer 1

The correct option is D The lac operon is induced.

• The lac operon is an operon required for the transport and metabolism of lactose in E.coli and some other enteric bacteria.
• It has three adjacent structural genes, lac Z, lac Y, and lac A.
• Lac operon is only induced in the presence of lactose and the absence of glucose.
• When E. coli is transferred to a medium containing only lactose as the sugar, lac operon will be induced to synthesize the enzymes necessary for the metabolism of lactose.

So, the correct answer is option D.