W - BIOL200 - 5.3-5.5, PROKARYORIC TRANSCRIPTION, EUKARYOTIC TRANSCRIPTION, RNA MATURATION
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26 Terms
Q: 3 stages of transcription?
A: Initiation, Elongation, Termination.
Q: Which enzyme transcribes RNA?
A: RNA Polymerase.
Q: Where does initiation happen?
A: Promoter (-35 box TTGACG, -10 box TATAAT).
Q: What binds the promoter?
A: Sigma factor + RNA Polymerase.
Q: What is the +1 site?
A: Start point for transcription.
Q: Consensus sequence?
A: Most common base pattern at -35/-10. Closer match = stronger Sigma binding.
Q: Direction DNA is read?
A: 3′→5′.
Q: Direction RNA is made?
A: 5′→3′.
Q: What happens in elongation?
A: Polymerase moves along DNA, adds RNA bases.
Q: What happens in termination?
A:
Rho-dependent: Rho binds RNA → knocks off polymerase.
Rho-independent: Hairpin loop + A-U region → polymerase falls off.
Q: Can prokaryotes transcribe and translate at same time?
A: Yes.
Q: Where is DNA in eukaryotes?
A: Chromatin (condensed with histones).
Q: What must happen for transcription?
A: DNA must be decondensed.
Q: Can transcription/translation happen at same time?
A: No — nucleus separates them.
Q: mRNA type in eukaryotes?
A: Monocistronic (one mRNA = one protein).
Q: 3 eukaryotic RNA Polymerases?
A: RNAP I (rRNA), RNAP II (mRNA), RNAP III (tRNA).
Q: Eukaryotic promoter element?
A: TATA box (~ -30 region).
Q: What recruits polymerase?
A: Transcription factors (TFs).
Q: What do enhancers do?
A: Increase transcription; can be far from promoter.
Q: What are the 3 pre-mRNA modifications?
A: 5′ cap, poly-A tail, splicing.
Q: What is the 5′ cap?
A: 7-methylguanosine → helps ribosome bind, protects RNA.
Q: What is the poly-A tail?
A: 100–250 A’s added to 3′ end → stabilizes RNA, export.
Q: What is splicing?
A: Removes introns, joins exons.
Q: What cuts introns?
A: Spliceosome (made of snRNPs).
Q: Key proteins in splicing?
A: snRNPs (small nuclear ribonucleoproteins).
Q: What is alternative splicing?
A: Same pre-mRNA → different mature mRNAs → different proteins.