Question

In the medium where E.coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose In the medium?

Answer 1

Lactose is the substrate for the protein beta-galactosidase and it controls turning on and of the operon. Consequently, it is called inducer.

The lac operon closes down some time after expansion of lactose in the medium in light of the fact that, as the process takes place the carbon source, for example, glucose is used, it prompts the non-availability of glucose.

If lactose is supplied to the medium which is devoid of carbon source, it is transported into the cell through the action of permease, as a result of which the repressor of the operon is synthesized and it gets attached with the operating region of the operon and inhibits the transcribing process of RNA polymerase.