Which statement correctly compares prokaryotic and eukaryotic transcription?

• A. Prokaryotes use three RNA polymerases; transcription occurs in the nucleus; translation is separated from transcription.
• B. Prokaryotes use a single RNA polymerase; transcription is coupled to translation; eukaryotes have three main RNA polymerases I, II, III; transcription occurs in the nucleus with processing before translation.
• C. Prokaryotes synthesize mRNA with introns; eukaryotes do not process mRNA.
• D. Both use the same RNA polymerases; both undergo nuclear processing.

Answer: (B)

Transcription in prokaryotes versus eukaryotes is defined by the RNA polymerase used, the cellular location of transcription, and the processing of the transcript. In bacteria, a single RNA polymerase handles transcription, and because there is no nucleus, translation can begin on the growing mRNA while it’s still being synthesized. In contrast, eukaryotes rely on three main RNA polymerases (I, II, and III); transcription happens in the nucleus, and the primary transcript must undergo processing—capping, splicing to remove introns, and polyadenylation—before the mature mRNA is exported to the cytoplasm for translation. The statement that describes these points—one RNA polymerase in prokaryotes, transcription coupled to translation, three RNA polymerases in eukaryotes, transcription in the nucleus with processing before translation—best reflects the fundamental differences. Other options either misstate the number of RNA polymerases in prokaryotes, or claim nuclear processing or coupling that doesn’t fit the biology of these organisms.