Question

Study the schematic representation of the genes involved in the lac operon given below and answer the questions that follow:

p

i

p

o

z

y

a

(a) The active site of enzyme permease present in the cell membrane of a bacterium has been blocked by an inhibitor, how will it affect the lac operon?

(b) The protein produced by the i gene has become abnormal due to unknown reasons. Explain its impact on lactose metabolism stating the reason.

(c) If the nutrient medium for the bacteria contains only galactose; will operon be expressed? Justify your answer.

Answer 1

(a) When the active site of enzyme permease present in the cell membrane of a bacterium has been blocked by an inhibitor, the lactose is not transported into the cell. As lactose is the inducer, the lac operon will not be switched on.

(b) Since the repressor protein synthesized by the i gene is abnormal, it will not bind to the operator region of the operon, resulting in a continuous state of the transcription process.

(c) No, because galactose is not an inducer it is a product of lactose metabolism.