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COMB 2001 CONSENSUS SEQUENCES ARE DESCRIBED WITH IUPAC AMBIGUOUS NUCLEOTIDE CODES
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COMB 2001 CONSENSUS SEQUENCES ARE DESCRIBED WITH IUPAC AMBIGUOUS NUCLEOTIDE CODES...
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COMB 2001 CONSENSUS SEQUENCES AREDESCRIBED WITH IUPAC AMBIGUOUS NUCLEOTIDE
CODES
What is a promoter? - ANSWER DNA sequence which RNA polymerase can bind
to and transcribe the protein
Prokaryotic promoters - ANSWER TATAAT -(10 region) 'Pribnow box'
TTGACA - (-35 region)
- two consensus sequences
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 the 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 methylation 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
URS - ANSWER URS & Silencer: repressor binding sites - repressor sites
UAS - ANSWER UAS & Enhancer: activator binding sites - Allows activators to
bind
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
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