An inducer in the lac operon is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Allolactose
The lac operon of E. coli has the genes for using lactose. A repressor protein, made all the time by the i gene, sits on the operator and keeps the operon switched off. An inducer is a substance that binds to the repressor and inactivates it. RNA polymerase can then transcribe the genes, and the operon is switched on.
(1) Allolactose — Correct. Lactose and allolactose act as inducers of the lac operon.
(2) Glucose — Incorrect. Glucose is formed when lactose is broken down, but it cannot act as an inducer. It is the preferred carbon source of the bacterium.
(3) Fructose — Incorrect. Fructose is not a part of lactose and does not act on the lac operon.
(4) Maltose — Incorrect. Maltose is a different sugar. It is not the substrate of beta-galactosidase and does not switch on the lac operon.
NCERT Extract:
The Lac Operon – …
