Gene expression Flashcards
What are two purines
Guanine
Adenine
What are the two pyrimidines
Thymine
Cytosine
What type of helical structure does RNA have
right handed
Is RNA more reactive or DNA and why
RNA- has 2’OH
What are all cellular RNA’s transcribed from
DNA templates
What is the production of RNA from DNA carried out by
DNA-dependent RNA polymerases
Whats the tole of RNA polymerase
Couples together ribonucleotide triphosphatases (NTPs: ATP, CTP, GTP, UTP)
Where does RNA polymerase work and what is it driven by
On DNA template
-driven by release and hydrolysis of PPi
What contains RNAP
All cells
Why is RNA synthesis easier in prokaryotes
RNA synthesis is initiated at DNA specific sites;
- expression involves small, single stand genome portions
- no primer needed and template fully conserved
what does the DNA serve as in prokaryotic transcription
Antisense/noncoding strand
What is the same sequence as sense/coding strand
RNA (except for T)
What are structural genes
Protein-coding genes
How are structural genes transcribed in eukaryotes
Transcribed individually
How are structural genes transcribed in prokaryotes
Transcribed together
where is transcription initiated
At a promoter
Where does RNAP bind
Initiation site through base sequence known as promoters
Where do promoters lie
Lies upstream of RNA’s starting molecule
In which direction does RNA synthesis proceed
5-3
What does the binding of the RNAP holoenzyme lead to
DNA ‘melting’ (separation) in its vicinity (transcription bubble)
What does the formation of. a transcription bubble allow
Allows complementary RNA strand synthesis
the bubble travels with RNAp
What does a processive RNA polymerase mean
Does not dissociate from template
When can protein synthesis begin before RNA is completely synthesized
In prokaryotes
How is transcription terminated in prokaryotes
DNA contains specific termination sites
What does the RNA transcript form
A self complementary hairpin
What does the self complementary hairpin do
Causes RNAP to pause
-permits RNAP conformational change allowing termination
What does the transcriptional machinery in eukaryotes require
Over 100 polypeptides to function
How are RNAP’s different in prokaryotes and eukaryotes
Greater mass in eukaryotes and greater subunit complexity
What are required for RNAP 2 transcription
General transcription factors
What are GTFs often targeted to and by what
TATA box by TATA binding proteins
What does RNAP 2 do
initiates RNA synthesis
After RNAP 2 initiates RNA synthesis, what does transcription machinery do
switch to elongation mode
What do eukaryotes lack
precise transcription termination sites
What does rifamycin B do
Inhibits only prokaryotic transcription
-prevents elongation
What does actinomycin D do
Binds to duplex DNA and inhibits DNA replication and transcription of eukaryotes and prokaryotes
-It interferes with polymerase passage
What does alpha-amanitin do
Tightly binds to RNAP 2 and blocks the elongation step
What do eukaryotes display more of than prokaryotes
pre-mRNA processing
What is RNA capping
RNA polymerase contains a CTD. When phosphorylated it recruits the Capping enzyme complex which modifies the 5’end
What does capping provide
Resistance to degradation and id of translation start site
What is polyadenylation and what does it do
Part of transcription termination
- influences mRNA stability
- prevents degradation when in a complex
What carries out splicing
spliceosomes
What are snRNAs
small nuclear RNA’s
