Which statement best describes RNA processing differences between eukaryotes and prokaryotes?

• A. Eukaryotes perform 5' capping, splicing, and 3' polyadenylation; prokaryotes generally do not process mRNA with introns or caps.
• B. Prokaryotes cap and polyadenylate all mRNA; eukaryotes do not cap or polyadenylate.
• C. Both process mRNA identically.
• D. Only eukaryotes do not perform splicing of introns.

Answer: (A)

RNA processing in eukaryotes includes adding a 5' cap, removing introns by splicing, and adding a 3' poly(A) tail. These steps are crucial for mRNA stability, export from the nucleus, and efficient translation. In contrast, prokaryotes generally lack introns to remove and do not add a 5' cap or a 3' poly(A) tail to their mRNA; transcription and translation often occur together in the cytoplasm, and mRNA is typically used without extensive processing. This makes the statement the best description of the differences: eukaryotes perform these processing steps, while prokaryotes do not process mRNA with introns or caps. The other options misstate the facts: prokaryotes do not cap and polyadenylate all mRNA; processing is not identical in the two groups; splicing is a feature of eukaryotic mRNA, not something absent only in prokaryotes.