NEET 2016 Biology Paper 1

Lactose acts as an inducer in lac operon. It binds with the repressor protein and thereby making the promoter site accessible to the RNA polymerase to initiate transcription of the lac operon.

Lac operon is an inducible operon. Lactose is the substrate for the enzyme β− galactosidase and it also regulates switching on and off of the operon. Hence, it is termed as inducer.