Answer: It binds to the repressor protein, preventing it from binding the operator.
- A It binds directly to RNA polymerase to switch on its activity
- B It binds to the repressor protein, preventing it from binding the operator
- C It binds directly to the operator sequence itself to block transcription
- D It enzymatically degrades the repressor protein into inactive fragments
Correct answer: B. It binds to the repressor protein, preventing it from binding the operator
Explanation: Allolactose (the inducer) binds the repressor protein, changing its shape so it can no longer bind the operator; this allows transcription of the structural genes.
Helicase unwinds the double helix at the replication fork; one new strand (leading) is synthesised continuously toward the fork, while the other (lagging) must be made in short, separate Okazaki fragments because DNA polymerase only adds nucleotides 5'→3'.
Concept context
DNA structure, replication, transcription, translation, the genetic code, and gene regulation (lac operon). The single most important chapter for NEET molecular biology.