Prokaryotic Transcription Flashcards
What’s transcription
making a complementary mRNA copy of DNA
Where does transcription occur
- in prokaryotes
- in eukaryotes
Cytosol (attached to DNA)
Nucleus
How many RNA p’s in
- prokaryotes
- eukaryotes
1/3
Describe promoter sequence
Highly conserved -35 and -10; 15-17 based apart which enables them to be in the same side of RNA
Describe important parts that are adjacent to the promoter sequence
Site between promoter and start codon?
initation site: +1; first program to be TRANSCRIBED
however this is not TRANSLATED - further up 5’ end is the coding segment (has start codon)
space between initation site and coding segment is called the 5’ unTRANSLATED region.
Describe initiation
Sigma factor of RNA polymerase binds to -35 and -10 region
Enhancer sequence binds transiently to RNA p, enabling elongation
Describe RNA p structure
Core enzyme has 5 subunits
Holoenzyme = come + sigma factor
Describe elongation
RNAp causes hydrolysis of ribonucleoside triphosphate into ribonucleoside monophosphate and pyrophosphate (which breaks down to 2 phosphate groups)
gives energy for strands to be separated and for RNAp to move along
travels in 3’ –> 5’ directin along template strand, synthesis mRNA in ‘–>3’ direction
Describe termination
Occurs when termination sequence is reached by intrinsic/rho dependent termination
Describe intrinsic termination
template DNA encodes hairpin followed by linear poly U
poly U is weak. RNA p attempts to backtrack but can’t because of looo, leading to release of everything
Describe Rho dependent termination
Before termination sequence, rho utilisation sequence encodes rho bonding site on RNA p
Then rho binds here when RNA p reaches termination sequence and stops moving
Rho binds to binding site on RNA p; everything dissociates
