Answer: Constitutive (continuous) expression of the z, y, and a genes regardless of lactose presence.
- A The operon would become largely switched off, even when lactose is present in the cell
- B Constitutive (continuous) expression of the z, y, and a genes regardless of lactose presence
- C Complete and total loss of RNA polymerase's ability to bind to the operon's promoter region
- D No change would occur, since the operator sequence does not affect transcription rates
Correct answer: B. Constitutive (continuous) expression of the z, y, and a genes regardless of lactose presence
Explanation: If the repressor cannot bind the mutated operator, it can no longer block RNA polymerase, so the structural genes would be transcribed constitutively, irrespective of whether lactose (inducer) is present.
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.