Which termination mechanism is used by prokaryotes?

• A. Prokaryotes use rho-dependent or independent termination.
• B. Prokaryotes terminate via polyadenylation signals.
• C. Termination occurs after capping and polyadenylation.
• D. Termination occurs only during translation.

Answer: (A)

Transcription termination in prokaryotes occurs by two main routes: rho-dependent and rho-independent termination. In rho-independent termination, the nascent RNA forms a GC-rich hairpin followed by a short run of uracils. This structure causes RNA polymerase to pause and dissociate from the DNA, releasing the transcript. In rho-dependent termination, the Rho protein binds a rut site on the growing RNA and uses energy from ATP to travel along the transcript toward the RNA polymerase, catching up to it and triggering release of the RNA.

The other options fit processes characteristic of eukaryotic gene expression or are related to translation rather than transcription. Polyadenylation signals and capping are part of mRNA processing in eukaryotes, not prokaryotic termination, and termination during translation involves stop codons and release factors rather than terminating transcription.