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.