Which protein binds to the operator region to prevent transcription in the lac operon?
The repressor protein binds to the operator region in the lac operon to block transcription in the absence of lactose. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.