CMB2001 Exam Questions With
Verified Answers
What is a promoter? - answerDNA sequence which RNA polymerase can bind to and
transcribe the protein
Prokaryotic promoters - answerTATAAT -(10 region) 'Pribnow box'
TTGACA - (-35 region)
- two consensus sequences
Prokaryotic RNA polymerase - answe...
Prokaryotic RNA polymerase - answer✔✔1 RNA Polymerase makes all 3 kinds of RNA
Composed of 5 subunits, four comprise the core enzyme
What is the core enzyme? - answer✔✔Helps to initiate and synthesize RNA. 4 main
polypeptides (2 alpha, 1 beta, 1 beta prime)
1 sigma bound only at initiation - forms holoenzyme
What is the purpose of the sigma subunit in RNA polymerase? - answer✔✔Binds to RNA
polymerase and allows core enzyme to transcribe specific sites at the promoter
Start site in prokaryotic promoters - answer✔✔TG/AT
+1
5-8bp
What is the span of the core/basal region of the eukaryotic promoter? - answer✔✔-30 (TATA)
(INR+1) to +30nt (DPE)
What elements are in the core region of the eukaryotic promoter? - answer✔✔TATA box
Inr (initiator)
DPE (downstream promoter element)
BRE (TFIIB recognition element)
Describe the TATA box consensus sequence - answer✔✔-31 to -26nt, TATAWAWR
Describe the Inr sequence - answer✔✔-2 to +4nt, YYANWYY with an A at +1
CpG islands - answer✔✔DNA regions rich in C residues adjacent to G residues. Especially
abundant in promoters, these regions are where methylation of cytosine usually occurs. - core
promoter elements
CpG islands are DNA methylations regions in promoters known to regulate gene expression
through transcriptional silencing of the corresponding gene
What is observed in core promoter CpG islands without obvious TATA and Inr sequences? -
answer✔✔Lower transcription rate, initiation at multiple start sites
What is the difference between a distal and proximal regulatory promoter element? -
answer✔✔Proximal = within 1kb of the start site
Distal = 1kb or more away from the start site
Negative gene regulation in prokaryotes - answer✔✔Operon in prokaryotes - on or off
Repressors can join to operon and block access to the promoter so RNA polymerase cannot join
and transcribe gene
Repressor gene further upstream and specific to repressor protein
... repressor activation is concentration dependent
How do you identify promoter elements via sequence comparison? - answer✔✔Analyse base
frequency within many genes to compare and identify a consensus sequence
How do you identify promoter elements via reporter analysis? - answer✔✔Insert a reporter gene
downstream of a regulatory sequence within a plasmid and measure expression of the reporter
protein.
The impact of mutations and control, induction, timing and location of transcription can be
measured by this.
Describe RNA polymerase I - answer✔✔Found in the nucleolus, it transcribes 28S, 18S and
5.8S rRNA
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