Question

In lac operon model, lactose functions as

Answer 1

The lac operon
The \(lac\) operon is an inducible operon system that remains usually in a repressed condition and gets activated only when the substance to be metabolised (lactose) is present.
Inducer
Inducer is a chemical which forms an inducer repressor complex. This prevents the repressor from binding to the operator gene.
Role of lactose in lac operon
The lactose acts as an inducer and binds to the repressor protein of \(lac\) operon. It inactivates the repressor and allows the RNA polymerase to bind to the promoter region. This allows transcription of the subsequent downstream structural genes.
Repressor
Repressor is a protein produced by the regulator gene (\(lac\) \(i\)) which binds to the operator region of the DNA to block the transcription.
Corepressor
Co-repressor is a molecule which along with repressor forms a complex and regulates gene expression. It helps to switch off \(lac\) operon.
Final answer
(C) Inducer that binds to repressor protein