11-19-08_transcriptionB - Barry: Rob, top five musical...

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Barry : Rob, top five musical crimes perpetuated by Stevie Wonder in the '80s and '90s. Go. Sub- question: is it in fact unfair to criticize a formerly great artist for his latter day sins, is it better to burn out or fade away? From High Fidelity (2000) A truly good book teaches me better than to read it. I must soon lay it down, and commence living on its hint. What I began by reading, I must finish by acting. Henry David Thoreau
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Announcements Quiz and review question answers will be put out this morning Review session tomorrow evening in ME 161 at 7:30 PM. Papers for written assignment 2, due 12/5/08, will also be posted this morning
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One in a million (billion), doc Three Steps That Give Rise to High-Fidelity DNA Synthesis REPLICATION STEP ERRORS PER NUCLEOTIDE POLYMERIZED 5′→3′ polymerization 1 × 10 5 3′→5′ exonucleolytic proofreading 1 × 10 2 Strand-directed mismatch repair 1 × 10 2 Total 1 × 10 9 Alberts et al., Molecular Biology of the Cell
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Correcting DNA spelling errors - "Instrumental in ruining entire operation for a Midwest chain store." DNA polymerase I (enzyme above left) has both 5'—>3' & 3'—>5' exonuclease activities, along with its polymerase activity For an incorrect nucleotide, the new end of the strand usually separates the 3’ to 5’ exonuclease undergoes a conformational change that directs the end of the newly synthesized strand into the 3'—>5' exonuclease active site, which removes the mismatched nucleotide 99% of errors corrected immediately (1 in 100 still not corrected)
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Base excision repair (BER) If a base has been incorrectly placed, it can be removed by DNA glycosylases. Glycosylases are specific for altered bases , such as uracil, 8- oxo-guanine, and 3-methyladenine Glycosylases cleaves glycosidic bond and removes base only , not nucleotide or nucleotide sequence as in NER. Glycosylases are specific for types of altered bases AP endonucleases break backbone next to baseless sugar phosphate
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More BER DNA polymerase β has dual actions: cleavage and synthesis First, cleavage of sugar-phosphate to leave hole in strand (step 4) Next, DNA polymerase β inserts proper complementary nucleotide (step 5) DNA ligase III repairs strand break (step 6)
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NER pathway Recognition of lesion through stalled RNA polymerase (transcription-coupled) or by a protein XPC (global) TFIIH is a transcription factor that participates in NER and in transcription initiation Subunits in TFIIH act as helicases to separate damaged strand (step 2) Segment containing error is cut out by
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This note was uploaded on 02/09/2010 for the course BIOL 230 taught by Professor Bartlett,e during the Fall '08 term at Purdue University-West Lafayette.

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11-19-08_transcriptionB - Barry: Rob, top five musical...

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