block b lec 1 Flashcards
(60 cards)
what is the least stable mRNA
bacterial mRNAs
what is being translated as mRNA is being synthesised
bacterial genes
what is to be said about transcription and translation
coupled
occurs at same time in same compartment
what do bacterial mRNAs lack
methyl-g caps
poly-a tails
what is the shine dalgarno seq
ribosome binding site
upstream of start codon
where is the promoter usually found
-10 and -35 elements
where are more highly expressed genes found
near oriC
what are operons
cluster of protein coding open reading frames transcribed as a single mRNA
where are operons expressed from
a single promoter
what are the individual coding regions in operons called
intercistronic regions
what are genes in a given operon are often related to
function
what does control of an operon do
control expression of entire function
what are coding sequences/OFRs transcribed as
polycistronic mRNA
what is transcription catalysed by
RNA polymerase
what does bacterial RNA polymerase do
unwind DNA to form a transcription bubble
what does the transcription bubble contain
ss non template DNA and the 8-9bp template DNA/RNA hybrid
what does RNAP do during RNA synthesis
moves along DNA while maintaining transcription bubble until end of RNA synthesis
structure fo RNAP core enzyme
5 subunits
a2bb’w
RNAP holoenzyme structure
a2bb’w(sigma)
core and sigma factor that recognises promoter seq
what forms the main catalytic centre in RNAP
B and B’
a2 role in RNAP
primary role is in RNAP assembly
role of w
non essential
what does RNA pol holoenzyme do
helps catalyse the opening of the DNA strands near the transcription start point
transcription initiation
what determines promoter specificity in RNA pol holoenzyme
alpha (sigma factor)
