Lecture 4 Exam 4

Lecture 4 Exam 4 - Biology 313 Lecture 38 Dec 3, 2010 -10...

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Biology 313 Lecture 38 Dec 3, 2010
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Transcription Unit Note: the transcript extends from the tx start site (+1) to the tx termination site, and includes the terminator +1 +10 -10
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3 stages of transcription process 1. Initiation 2. Elongation 3. Termination
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Bacterial transcription: the paradigm Initiation : binding of transcription apparatus to promoter is responsible for determining the frequency of tx of a certain gene and where the tx start site is Bacterial promoters: have consensus sequences : short stretches of nucleotides that are “conserved” in sequence among a large number of genes and/or organisms
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A generic consensus sequence -- is this labeled correctly?
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Initiation: bacterial promoters 10 consensus (Pribnow box) : 10-15 bp upstream of start site = 5’—TATAAT—3 35 consensus sequence = 5’—TTGACA—3’
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Initiation Core + σ ( holoenzyme) binds to -10 and -35 promoter elements (“weak binding”)
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Initiation Weak binding causes a conformational change of holoenzyme and tight binding. This positions the RNA polymerase over the start site (+1) and causes the DNA (from -10 to +2) to unwind (transcription bubble is formed). +1 transcription bubble
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Initiation rNTPs are added to 3’end of growing RNA strand (no primer is needed) +1
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Elongation RNA polymerase changes conformation and moves downstream from the promoter. σ is released and RNA polymerase moves down the template strand synthesizing the growing RNA molecule from its 3’-end
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Termination
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Transcription Terminator is a hairpin that causes RNA Polymerase to pause How destabilize RNA-DNA duplex? Following the hairpin is a
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This note was uploaded on 10/06/2011 for the course BIO 313 taught by Professor Rodermel during the Spring '11 term at Iowa State.

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Lecture 4 Exam 4 - Biology 313 Lecture 38 Dec 3, 2010 -10...

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