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lecturenoteschap21-10-1slide - BCMB 3100 - Chapter 21...

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BCMB 3100 - Chapter 21 Transcription & RNA Processing efinition of gene Definition of gene RNA Polymerase Gene coding vs template strand romoter Promoter Transcription in E. coli Transcription factors RNA processing mRNA processing
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Biological information flow
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_______ - a DNA sequence that is transcribed (includes genes that do not encode proteins) ______________________ ” encode t i RNA ti l f l proteins or RNA essential for normal activities of the cell (e.g. enzymes in basic etabolic path a s tRNAs and rRNAs) metabolic pathways, tRNAs and rRNAs)
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Four Classes of RNA in living organisms ( review ) essenger RNA RNA near “copies” of DNA that encode Messenger RNA ( mRNA ) - linear “copies” of DNA that encode genetic information. Encode primary structure of protein. ~1-3% of total RNA, relatively unstable (discovered by Jacob & Monod). Non-coding RNA Ribosomal RNA ( rRNA ) - ~80% of total RNA, part of ribosomes ,p (translation machinery) Transfer RNA ( tRNA ) - ~15% of total RNA, 73-95 nucleotides long, carry activated amino acids to ribosomes during translation (Small RNA) - may have catalytic activity and/or associate with proteins to enhance activity, some involved with RNA processing (includes snRNA and microRNA, the latter involved in mRNA degradation, translation inhibition and chromatin remodeling), (long non-coding RNAs (long ncRNAs)): functions being determined.
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NA Synthesis ( col i RNA Synthesis ( E.coli ) Transcription NA  NA DNA  RNA NA Polymerase (450 kd) ( 960 Hurwitz; Weiss RNA Polymerase (450 kd) ( 1960, Hurwitz; Weiss ) (recognizes promoter & (binds DNA template) & initiates synthesis) 2   (holoenzyme) rms phosphodiester bond forms phosphodiester bond binds rNTPs (see Table 21.2 & Fig. 21.2) 2  (core enzyme)
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RNA Synthesis 1) Intiation NA polymerase is 2) Elongation RNA polymerase is responsible for these function in RNA 3) Termination synthesis E. coli RNA polymerase synthesizes all ajor types of RNA: major types of RNA: mRNA, tRNA, rRNA, small RNA
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Transcription in E.coli ) RNA polymerase searches for initiation sites ( 2000 in 1) RNA polymerase searches for initiation sites (~2000 in 4,000,000 bp) ) U i d DNA t d i l d d t l t 2) Unwinds DNA to produce single-stranded template 3) Selects correct ribonucleotide and catalyzes the formation of phosphodiester bonds (totally processive) 4) Detects termination signals 5) Interacts with activators & repressor proteins
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Requirements for Transcription DNA template Note: RNA RNA polymerase Transcription factors Polymerase does NOT require a rimer. RNA chains NTPs (ATP,CTP,GTP,UTP) + primer. RNA chains can be initiated de novo. Mg ++ Mechanism of elongation is the same as for DNA Polymerase: nucleophilic attack by 3’-OH on - hosphate of NTP phosphate of NTP
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Fig 21.3 NA polymerase RNA polymerase reaction
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Fig 21.3 (cont) E.coli transcription te: 30- 5 rate: 30 85 nucleotides/sec Error rate = 10 -6 RNA Polymerase as no exonuclease has no exonuclease activity
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ig 21 5 rientation of a gene Fig 21.5 Orientation of a gene
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Fig 21.6
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lecturenoteschap21-10-1slide - BCMB 3100 - Chapter 21...

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