Using the car analogy for regulation of gene expression in which negative control is exerted by setting the parking brake and positive control occurs by stepping on the gas pedal, which answer best defines a component of lac operon control?

a. inducer (lactose) = acts by stepping on the gas pedal

b. cap binding site = part of gas pedal

c. repressor = releases the parking brake

d. operator = part of the gas pedal

The correct answer is a inducer(lactose) = acts by stepping on the gas pedal.

Explanation:

In lac operon lactose act as an inducer.Lactose exerts its action by binding with the repressor and inducing a conformation al change in the repressor molecule and prevent the later from binding to the operator region.

   This ultimately result in the expression of the structural genes such as Lac Z ,Lac Y and Lac A.

  According to the given question if the lac operon is described using a car analogy then the inducer lactose will act by stepping on the the gas pedal and this is the positive regulation of Lac operon.

the correct answer is b