BCHM 4116 1st Edition Lecture 23 Outline of Last Lecture I Mutations Outline of Current Lecture I Genes Transcribed of Gene Expression II Transcription has 4 stages Current Lecture Chapter 29 Transcription and Regulation of Gene Expression 1 29 1 Genes Transcribed in Prokaryotes a RNA pol 2 i ii 2 large subunits 1 performs most of enzymatic function iii Binding of subunit recognizes diff DNA sequences that act as promoters 1 Promoters identify transcription start site b Transcription has 4 stages i Binding of RNA pol at promter site subunit recognizes promoter sequence 1 RNA pol promter form a complex 2 3 AKA closed promoter complex b c dsDNA is not opened 4 1 transcription start site 5 within promoter are 2 consensus sequences a Pribnow box 10 region i TATAAT b 35 region subunit recognizes and binds to 10 35 regions 6 ii Initiation of polymerization 1 RNA pol does not require primer subunit dissociates from RNA pol once 9 12 resides long has 2 been formed completion of initiation core RNA pol highly processive and goes on to synthesize 3 remainder of mRNA iii Chain elongation These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 Catalyzed by core polymerase 2 To prevent torsional stress from inhibiting transcription gyrase introduces negative supercoils thereby remove positive supercoils ahead of RNA pol 3 Topoisomerase removes negative supercoil behind DNA iv Chain termination 1 Bacteria a Intrinsic termination i Specific sequences in DNA called termination sites 1 Inverted repeats typically G C rich so forms stem loop structure 2 Nonrepeating segment that punctuates inverted repeats 3 6 8 A s in DNA coding for U s in transcript b Rho factor i Less common mechanistically more complex ii ATP dependent hexameric helicase iii Catalyzes unwinding of RNA DNA duplex iv Rho factor recognizes and binds to C rich region then advances in 5 3 direction until reaches transcription bubble v There it catalyzes unwinding of transcript and template releasing RNA chain
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