Central dogma and transcription sheet5-mark answer frameDescribe the process of transcription in bacteria. Explain how the primary transcript is processed in eukaryotes.
How to lay out the answer. Follow the frame, then write it in your own words.
- 1 · Define transcription. Copying of the information in one DNA strand into RNA; the first step of the central dogma.
- 2 · Describe the transcription unit. Promoter, structural gene and terminator; template strand 3′→5′, coding strand 5′→3′.
- 3 · Draw the transcription unit. [Diagram: promoter, structural gene, terminator, template and coding strands with polarity]
- 4 · Give the three stages in bacteria.
- Initiation: RNA polymerase with σ binds the promoter.
- Elongation: ribonucleoside triphosphates added by base pairing.
- Termination: ρ factor; RNA and enzyme fall off at the terminator.
- 5 · Name the eukaryotic polymerases. I: rRNAs; II: hnRNA; III: tRNA, 5S rRNA, snRNAs.
- 6 · Explain processing. Splicing removes introns; capping adds methyl guanosine triphosphate at 5′; tailing adds 200 to 300 adenylates at 3′.
- 7 · Close in one line. So bacteria use their mRNA at once, while eukaryotes process hnRNA into mRNA before it leaves the nucleus.
Scoring tip: Name the sigma and rho factors, and give all three processing steps. Each carries a mark.
