In bacteria, what occurs after promoter escape during transcription initiation?

• A. Ribosome binds to nascent RNA.
• B. RNA synthesis stops.
• C. DNA rewinds.
• D. Sigma factor is often released after promoter escape.

Answer: (D)

In bacteria, the switch from initiation to elongation happens when the RNA polymerase clears the promoter. At that moment, the sigma factor, which helped the enzyme recognize the promoter and start transcription, is often released. This release lets the core RNA polymerase proceed smoothly along the DNA to produce a longer RNA transcript without the promoter-specific contacts that were important for initiation.

Ribosome binding to nascent RNA touches on translation, which occurs after transcription has begun and isn’t the defining step right after promoter escape. RNA synthesis doesn’t stop once promoter escape happens; it continues as elongation proceeds. The DNA behind the moving polymerase does re-anneal as the transcription bubble passes, but that re-winding isn’t the key event marking the transition to elongation—the release of the sigma factor is.