transcription by prokaryotic RNA polymerases Flashcards
what occurs during initiation?
promoter binds upstream from the gene to form a closed complex, transcription bubble forms
what occurs during elongation?
mRNA is made from the RNAP. transcription bubble moves along the DNA and RNA chain is extended in the 5’-3’ direction, nucleotides are added to the 3’ end
what happens during termination?
DNA duplex reforms as the RNAP dissociates at a terminator site
what is position +1?
the first base to be copied into mRNA
which DNA strand contains the promoter?
coding strand
how is the RNA synthesised?
the 3’ OH on the last nucleotide reacts with an incoming nucleoside triphosphate, which loses its two terminal phosphates y and B, its a-phosphate is used in the phosphodiester bond
what is base stacking?
where the polarisation of moecules with an aromatic ring like Phe or Tyr causes depolarisation to be spread across whole molecule. stabilises the helix
what causes base flipping?
constant attack of the DNA helix from other molecules due to brownian motion
what feature of the major groove allows promoters to find DNA?
different base-pairs have different groups of donors, acceptors and hydrophobic groups protruding into the major groove
what are the products of transcription?
dsDNA, ssRNA, PPi
why does initiation of transcription need so much regulation?
no primer to bind to, must be very precise to read the promoter accurately
how does prokaryotic RNA synthesis differ from eukaryotic synthesis?
- synthesis is de novo
- synthesis does not require a primer
what characteristic tag is found at the 5’ end of newly synthesised RNA?
first base is either pppG or pppA
what is the UP element? what is its role?
a sequence present roughly 40-60 nucleotides away from the transcriptional start site. bound to a-subunit of RNAP and functions to increase efficiency of transcription by creating an additional binding site for the polymerase
