In the lac operon, when lactose is absent,

  1. β-galactosidase is made
  2. RNA polymerase transcribes lacZ
  3. lactose binds the repressor
  4. the repressor binds to the operator and blocks transcription
Answer

D) the repressor binds to the operator and blocks transcription

No lactose = genes off. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

Biology MCQ · More A Level Biology: Inheritance MCQs · Practise