In the lac operon model, what is the primary role of the allolactose molecule?

Correct option is A

The correct answer is: (a) It functions as an inducer, binding to the repressor protein and inactivating it.
Explanation:
· In the lac operon model of E. coli, allolactose (an isomer of lactose) acts as an inducer.
· It binds to the repressor protein (LacI), causing a conformational change that prevents the repressor from binding to the operator.
· This allows RNA polymerase to transcribe the structural genes (lacZ, lacY, lacA) for lactose metabolism.
Information Booster:
· The lac operon is a classic example of inducible operon.
· Discovered by François Jacob and Jacques Monod (1961).
· lacZ → β-galactosidase (breaks lactose → glucose + galactose).
· lacY → Permease (helps lactose enter the cell).
· lacA → Transacetylase (detoxifies by-products).
Additional Knowledge:
· (b) Incorrect → Corepressors usually enhance repression (e.g., tryptophan in trp operon).
· (c) Incorrect → Promoter binding is by RNA polymerase, not allolactose.
· (d) Incorrect → Allolactose is not a gene; it doesn’t code for enzymes.