Prokaryotic Transcription Flashcards
Why are sigma H and E required and what are they encoded by?
H - heat shock (rpoH)
E - extreme heat shock (rpoE)
Sigma F, S and N are encoded by what and used for what?
fliA - flagellar based motility
rpoS - stationary phase adaptation
rpoN, glnF - nitrogen-regulated
Why are there specific sigma factors?
Different genes have different promoters (bind specific sigma factors)
Bacterial cell can respond to specific situation e.g. in stress S can often take over to a degree.
what is abortive initiation?
After growing to 10nts RNA meets physical block (3.2 loop of sigma subunit), preventing new mRNA leaving exit channel.
Transcription stops and 10 nt chain of mRNA released.
what was the traditional view concerning operons?
that structural genes within an operon were functionally related.
What are the equations for prokarytoic elongation of transcription and gow fast is it?
RNAn + NTP –> RNAn+1 + PPi
30 to 100 nts a second
Secondary structure causes pauses - GreA and Gre proteins remove blackages.
What is the equation for prokaryotic amino acid activation?
AA + tRNA –> aminoacyl-tRNA
Catalysed by aa-tRNA synthetase and using ATP.
What is encoded by rpoD?
sigma70 - housekeeping genes.
What is transcription ?
The process by which ssRNA with base sequence complementary to template strand of DNA is synthesised.
What is translation?
Process by which genetic message carried by mRNA directs synthesis of polypeptides.
What are prokaryotes?
Cells with genetic info not enclosed by membranes
Bacteria and archaea.
What is significant concerned no aminoacyl tRNA synthetase?
Specific for each tRNA.
Why do only tRNA molecules know the ‘true genetic code’?
Protein synthesis only recognises anticodon of charged tRNA and can’t tell if adding correct AA.
