the repressor protein of the lac operon is constitutively synthesised from the i gene (regulator gene) . This repressor protein binds to the operator region of the operon, which prevents RNA polymerase from transcribing the structural genes . This process effectively switches off the operon in the absence of an inducer like lactose . This mechanism is a classic example of negative regulation . Mastering these operon mechanics is essential, as NCERT textbooks are the primary resource for approximately 95% of NEET Biology questions .