Q.Why does bacterial mRNA require little or no post-transcriptional processing, while eukaryotic hnRNA requires extensive processing before it can be translated?

Step 1. Bacteria have no nuclear membrane separating their DNA from their ribosomes, so a newly transcribed mRNA is generally translated at the ribosome directly and immediately, often even while transcription of that same molecule is still ongoing.

Step 2. Because translation begins essentially as soon as (or before) transcription finishes, there is no time or physical need for extensive further modification of bacterial mRNA — it is used essentially as-is.

Step 3. Eukaryotic cells DO have a nuclear membrane, physically separating the nucleus (where transcription occurs) from the cytoplasm (where translation occurs at the ribosome).

Step 4. Because eukaryotic RNA must be exported out of the nucleus before it can be translated, and because the primary transcript (hnRNA) includes non-coding introns, it must first undergo processing — splicing, capping and tailing — before it is a mature, translatable mRNA ready for export.

Connect the STRUCTURAL difference (no nucleus in bacteria vs a nucleus in eukaryotes) directly to the FUNCTIONAL difference (immediate translation vs required processing + export).

• Saying bacteria have NO post-transcriptional processing at all — the point is they need comparatively LITTLE (not literally zero) processing, mainly because translation begins so quickly.