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25 Cards in this Set
- Front
- Back
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transcription
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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) |
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transcription is the RNA polymerase-catalyzed synthesis of RNA from a DNA template
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direction of transcription:5-3
direction of reading of template DNA:3-5 |
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important features of transcription
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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 |
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overview of transcription
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RNA pol with sigma factor makes haloenzyme (sigma aids in recognition of promotor and initiation site)
transcription begins and sigma is released |
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overview of transcription continued...
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RNA chain growth
termination site reached release of pol and RNA |
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sigma promotors
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70 housekeeping:-35...-10 +1AT
54 N regulated:-24...-12 +1AT 32 heat shock response:-35...-10 +1AT |
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bacterial RNA polymerase complexes
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core enzyme->promotor enzyme with holoenzyme->elongation complex
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template and coding strands
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5'coding
3'template 5'RNA <-upstream....downstream-> |
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transcription termination in prokaryotes
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(factor-independent and dependent)
independent:CG rich loop dependent:termination prot moves toward 3' of RNA(need enzyme) |
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factor independent transcription termination in prokaryotes
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DNA with inverted repeats
transcription of 1 strand RNA fold to form 2ndary structure stemp-loop in RNA immediately upstream from a run of U's leads to termination |
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factor dependent transcription termination
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rho termination site
RNA pol use rho helicase that unwinds RNA-DNA duplex rho binds with RNA pol near termination site |
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unit of transcription:operon
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(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 |
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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 |
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antibiotics that inhibit transcription
(rifampin) |
a macrocyclic lactone that binds to the b-subunit of RNA pol of bacteria, mito, and chloroplasts.
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antibiotics that inhibit transcription
(actinomycin D) |
binds to the major groove of DNA in GC rick regions, inhibits transcription and replication
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transcription in eukaryotes
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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) |
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overview of mRNA processing in eukaryotes
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pre-mRNA->(5'cap,3'polyadenylation)
introns cut mRNA-> (translation) protein |
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initiation of transcription in eukaryotes
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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) |
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initiation of transcription in eukaryotes
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enhancer sequences:stimulate
silencer sequences:repress both are present at remote sites as one or multiple copies, function unpstream or downstream of genes. |
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termination of transcription in eukaryotes.
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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 |
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capping of pre-mRNA transcripts in eukaryotes
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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 (STEPS REQUIRED FOR RECOGNITION OF THE RNA BY RIBO AS MRNA) |
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RNA splicing
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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) |
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summary of mRNA processing in eukaryotes
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coding strand(DNA) 3-5
noncoding (introns) transcription 5-3 pre-mRNA 5-3 cap and poly(A)tail ribozymes 5-3 mRNA (only exons) thru nucleoplasm into cytosol |
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self-splicing introns
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RNA of introns folds into an active site
only kind know in bacteria and bacteriophage |
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RNA editing
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mito and chloro RNA:
cytidine,uridine (hexagons) UTR and 2dary sturcture modifications of nuclear RNA adenosine,inosine (hex,pent) |
