Question

Choose the correct answer from the alternatives given.
The lac operon is transcribed when

• A. lactose is needed by the cell
• B. lactose is available to the cell
• C. lactose is unavailable to the cell
• D. lactic acid is available to the cell

Answer 1

Answer: (B)

The lac operon is an example of an inducible operon which is required for transportation and metabolism of lactose sugar. The availability of the lactose in the cell initiates the transcription to express the three genes of this operon i.e. lacZ, lacY, and lacA genes. The translation of these genes produces three enzymes. LacZ gene produces beta-galactosidase which cleaves lactose into glucose and galactose. LacY gene produces permease enzyme to allow lactose to enter the cell while the lacA gene produces transferase enzyme.

So, the correct option is 'lactose is available to the cell'.