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25 Cards in this Set

  • Front
  • Back
transcribe info in nucleotide sequence from one strand into RNA.
if info is prot assembly then transcript is mRNA
some genes are transcribed and never translated (rRNA,tRNA)
transcription is the RNA polymerase-catalyzed synthesis of RNA from a DNA template
direction of transcription:5-3
direction of reading of template DNA:3-5
important features of transcription
begins at nucleo sequences (promotors)
in prok: promotors are adjacent to DNA site
in euk:promotors are complex, involve enhancers
in prok:transcription stops at termination
in euk:transcription stops by slow diffusion by ancillary events
overview of transcription
RNA pol with sigma factor makes haloenzyme (sigma aids in recognition of promotor and initiation site)
transcription begins and sigma is released
overview of transcription continued...
RNA chain growth
termination site reached
release of pol and RNA
sigma promotors
70 housekeeping:-35...-10 +1AT
54 N regulated:-24...-12 +1AT
32 heat shock response:-35...-10 +1AT
bacterial RNA polymerase complexes
core enzyme->promotor enzyme with holoenzyme->elongation complex
template and coding strands
transcription termination in prokaryotes
(factor-independent and dependent)
independent:CG rich loop
dependent:termination prot moves toward 3' of RNA(need enzyme)
factor independent transcription termination in prokaryotes
DNA with inverted repeats
transcription of 1 strand
fold to form 2ndary structure
stemp-loop in RNA immediately upstream from a run of U's leads to termination
factor dependent transcription termination
rho termination site
RNA pol
use rho helicase that unwinds RNA-DNA duplex
rho binds with RNA pol near termination site
unit of transcription:operon
(a segment of DNA thats transcribed into RNA)
in pro and euk the rRNA are co-transcribed and mature RNAs are produced by processing of primary transcript.
in prok:1mary is mRNA, the RNA isnt cleaved unless it has introns.Translation starts and stop codons specify the start/end of polypeptides
antibiotics that inhibit transcription
(w/ target or action)
streptolydigin b of RNA pol
actinomycin D binds DNA
rifampin b of RNA pol
bleomycin cuts DNA
antibiotics that inhibit transcription
a macrocyclic lactone that binds to the b-subunit of RNA pol of bacteria, mito, and chloroplasts.
antibiotics that inhibit transcription
(actinomycin D)
binds to the major groove of DNA in GC rick regions, inhibits transcription and replication
transcription in eukaryotes
euk have 3 diff RNA pol that transcribe diff genes:
rRNA(28,18,5.8): pol I (in nucleolus)
mRNA&nuclear RNA: pol II(nucleoplasm)
tRNA,5 rRNA: pol III (nucleoplasm)
overview of mRNA processing in eukaryotes
introns cut
mRNA-> (translation)
initiation of transcription in eukaryotes
on DNA, promotors are large:
@ -25, TATAbox is for initition
bw -50&-200 another promotor proximal element is needed
(CAAT @ -70, GC box @ -90)
assisting the RNA pol in forming an initiation complex as basal transcription factors (TFIIA,TFIIB,TFIIC)
initiation of transcription in eukaryotes
enhancer sequences:stimulate
silencer sequences:repress

both are present at remote sites as one or multiple copies, function unpstream or downstream of genes.
termination of transcription in eukaryotes.
poly(A) addition signal causes to cleave RNA and poly(A) tail is added to transcript.The poly(A) consensus is AAUAAA
PAP:polyA polymerase
about 50-250 A are added to the 3' end of the transcript
capping of pre-mRNA transcripts in eukaryotes
spliced precursor mRNA is processed to become mature mRNA
poly(A)added to 3'
5' is capped
7-methyl G added to end in unusual 5-5 linkage
sugar of bases at 5' of message are methylated at the 2' position
RNA splicing
in euk occurs in nucleus by spliceosomes(spliceosomes:several prot and small RNA cofactors ie SNRP)
assemble spliceosome
cutting 5' splice site
cutting 3' splice site
intron separate from exons(2)
summary of mRNA processing in eukaryotes
coding strand(DNA) 3-5
noncoding (introns)
5-3 pre-mRNA
5-3 cap and poly(A)tail
5-3 mRNA (only exons)
thru nucleoplasm
into cytosol
self-splicing introns
RNA of introns folds into an active site
only kind know in bacteria and bacteriophage
RNA editing
mito and chloro RNA:
cytidine,uridine (hexagons)
UTR and 2dary sturcture modifications of nuclear RNA
adenosine,inosine (hex,pent)