KCET 2018 Biology Solved Paper

The lac operon is an example of an inducible operon which induces transcription of structural genes in the presence of lactose or allolactose and hence it is called an inducer. The regulator i gene codes for active repressor protein but lactose or allolactose binds to the repressor protein and inactivates it thereby preventing it from binding to the lac operator. RNA polymerase can now access the promoter and transcribe the structural genes. Enzymes needed for using lactose are made.