NEET BIOLOGY

Detailed explanation-1: -Solution : Lactose <br> Detailed Answer: <br> Lactose is known as inducer in lac operon because it controls switching on and switching off of operon.

Detailed explanation-2: -Two regulators turn the operon “on” and “off” in response to lactose and glucose levels: the lac repressor and catabolite activator protein (CAP).

Detailed explanation-3: -So, the correct answer is ‘Regulator gene.

Detailed explanation-4: -Regulation of the lac Operon The activity of the promoter that controls the expression of the lac operon is regulated by two different proteins. One of the proteins prevents the RNA polymerase from transcribing (negative control), the other enhances the binding of RNA polymerase to the promoter (positive control).

Detailed explanation-5: -i) Lactose is the substrate for the enzyme -galactosidase and regulates switching on and off of the operon. ii) Lac operon consists of three regulatory genes. iii) Lac operon consists of one structural gene. iv) Regulation of lac operon by repressor is referred to as positive regulation.