DNA transcription Flashcards
what enzyme transcribes mRNA? in what direction?
how is RNA polymerase II different to DNA polymerase III?
what will the mRNA be coding?
RNA polymerase II- 5’ to 3’
doesn’t need a primer
it’s complimentary to the template strand so it’s the sequence of the coding strand
PROKARYOTIC GENE FOR TRANSCRIPTION
where does transcription begin?
what is upstream of this site?
what is downstream?
what are the 2 important sequences on a prokaryotic gene?
what are they? and what do they do?
at the start point (+1)
promotor region - control region for main body of gene
the DNA to be transcribed into mRNA (or pre-mRNA)
-10 sequence & -35 sequence
consensus sequences & signal to RNA polymerase to bind
EUKARYOTIC GENE FOR TRANSCRIPTION
what is downstream of the start point?
what is upstream?
what is the promotor region?
what binds to the control/enhancer elements? what does this do?
gene for transcription containing both introns & exons (both present in pre-mRNA)
promotor & control/enhancer elements
TATA box (-25)
transcription factors- increase basal levels of transcription
What are eukaryotic genes called? what does this mean?
What about prokaryotic genes?
LAC OPERON IN E.COLI (controlling transcription in prokaryotes)
what is the preferred substrate in the e.coli?
what does Lac-Z encode?
Lac-Y?
Lac-A? Why is this important?
what happens if levels of glucose & lactose are high?
glucose is high but lactose is not?
lactose is high & glucose is not?
monocystronic genes- each gene has its own promotor which transcribes the gene into discrete mRNA which is translated into discrete proteins
polycystronic genes- lots of genes are controlled by 1 promotor/operon- producing 1 piece of mRNA which is then translated into several discrete proteins
glucose
beta galactosidase - catalyses lactose to glucose & galactose
permease - inserts into cell membrane & transports lactose across
thiogalactoside transacetylase - rids cell of toxic thiogalactosides. transporting lactase across cell membrane allows toxins to also be imported- rids cell of this.
lactose binds to repressor to stop repressor binding to operator & allows RNA polymerase to promotor region = basal level transcription
there is no lactose to bind to the repressor- so there is no mRNA transcription
lactose binds to repressor & cAMP binds to CAP site & to RNA polymerase for a tighter complex & more enhanced levels of mRNA transcription
EUKARYOTIC CONTROL OF TRANSCRIPTION (PIC COMPLEX)
what is the enhancer/control region called & where is it in respect to the startpoint?
what are the steps for forming the PIC complex?
how is this complex activated after formation?
what kind of level of transcription is this?
what enhances this level in eukaryotes? how do they do this?
what else can bind to these molecules?
TATA - upstream of startpoint
- TFIID to TATA
- A & B
- F & RNA polymerase II
- E & H
hydrolysis of ATP (into AMP & 2Pi) phosphorylates the tail of RNA polymerase II - allows it to escape promotor & transcribe
basal level
activator proteins- bind to enhancer sequence on DNA & cause DNA to bend so the PIC complex are bound more tightly upstream the promotor region
coactivators
what 2 domains do a transcriptional factor have?
why is there a lot of diversity in DBDs?
what 3 domains do gluococorticoid receptors have?
how is it retained in the cytosol?
what happens when hormone enters the cytosol?
how is transcription tissue specific?
what is a cis element & a trans factor?
DNA binding domain, activation domain
distinctive structural shapes allow DBDs to interact with different grooves on DNA
DBD, activator domain, ligand binding domain
inhibitors bind to the LBD
hormone has greater affinity for LBD- binds to LBD to displace inhibitors & allows GR to translocate into nucleus for transcription (DBD binds to target sequence on DNA)
certain cell nuclei (e.g liver nuclei) contain regulatory transcription factors that bind to upstream control/enhancer elements on DNA which other cell nuclei (e.g brain nuclei) won’t contain = results in enhanced transcription in liver but basal in brain
cis element = upstream enhancers on same chromosome as gene
trans factor = DNA binding protein from another site
what are the 4 steps for making mRNA from pre-mRNA?
- 5’ end is capped by 7-methylguanosine (prevents endonuclease degrading pre-mRNA)
- 3’ poly(A) site is cleaved with endonuclease
- polyadenylation with poly(A) polymerase & ATP to add adenosine100-250 at 3’
- splicing of introns
