11-9-09_transcription

11-9-09_transcription - A truly good book teaches me better...

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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 I hope that someone gets my I hope that someone gets my I hope that someone gets my Message in a cell, yeah Message in a cell, yeah -adapted from the Police
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Announcements Papers for written assignment 2 due 12/4/09 Quiz 7 is available and is due this Wednesday at 5 pm. It covers photosynthesis. Quiz 8 will be made available this Tuesday (11/10) and will be due the following Monday (11/16). It will cover DNA structure, replication, and repair. Exam 1 copies will be thrown out at the end of this week (11/13/09). They are available in MJIS 2019 from 8:30- 3:30 M-F. Neuroscience lecture, “Useful signals in motor cortex”, Andrew Schwartz, STEW 322, 3:30 today
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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 two endonucleases (steps 3 and 4) DNA polymerases δ and ε put back the proper DNA sequence (step 5) DNA ligase joins the newly synthesized ends (step 6)
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Genetic text messaging From DNA to mRNA: Transcription
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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.

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11-9-09_transcription - A truly good book teaches me better...

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