In prokaryotes, what triggers transcription termination?

In prokaryotes, what triggers transcription termination?

• A. DNA terminator sequence
• B. Polyadenylation signal
• C. Rho factor
• D. Spliceosome assembly

Answer: (A)

In bacteria, transcription termination is triggered by signals encoded in the DNA called terminators. When these signals are transcribed, they often form a hairpin structure in the RNA followed by a short stretch of uracils. This hairpin destabilizes the RNA–DNA pairing in the transcription complex, prompting RNA polymerase to dissociate and release the transcript. There’s also a separate, protein-driven pathway where the Rho factor helps terminate transcription, but that relies on a specific RNA sequence (rut site) rather than a DNA terminator signal. The other options describe processes specific to eukaryotes or a different termination mechanism, so they aren’t the direct triggers in prokaryotes.

In bacteria, transcription termination is triggered by signals encoded in the DNA called terminators. When these signals are transcribed, they often form a hairpin structure in the RNA followed by a short stretch of uracils. This hairpin destabilizes the RNA–DNA pairing in the transcription complex, prompting RNA polymerase to dissociate and release the transcript. There’s also a separate, protein-driven pathway where the Rho factor helps terminate transcription, but that relies on a specific RNA sequence (rut site) rather than a DNA terminator signal. The other options describe processes specific to eukaryotes or a different termination mechanism, so they aren’t the direct triggers in prokaryotes.