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?
Lac operon is a section of DNA this is made from 3 adjoining structural genes, namely, an operator gene, a promoter gene, and a regulator gene. It works in a coordinated way to metabolize lactose into glucose and galactose. In lac operon, lactose acts as an inducer. It binds to the repressor and inactivates it. Once the lactose binds to the repressor, RNA polymerase binds to the promoter region. Hence, 3 structural genes explicit their product and respective enzymes are produced. These enzymes act on lactose in order that lactose is metabolized into glucose and galactose. After sometime, while the extent of inducer decreases as it's far absolutely metabolized with the aid of using enzymes, it reasons synthesis of the repressor from regulator gene. The repressor binds to the operator gene and stops RNA polymerase from transcribing the operon. Hence, the transcription is stopped. This sort of law is called terrible law.
