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lecture 37 - Lecture 37 Wed What is covered in the Final...

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Lecture 37. Wed. 4-27-11
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Section 1 information Section 2 information Section 3 information Lab information Exam 1 Exam 2 Final Exam Exam 3 What is covered in the Final Exam? Lab Exam 100 points 70 points 100 points 100 points
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DNA damage and repair
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Cell choices when DNA is altered by damage, mutation or mistakes: 1. Correct it. Arrest the cell cycle and clean up the mess before proceeding. 2. Evolve. Live with the change as a good mutation and as a selective advantage 3. Cell suicide ( apoptosis ) 4. Die ( necrosis ) because there is no choice 5. Cancer
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DNA Repair Some examples of DNA repair mechanisms: 1. Proofreading by DNA polymerase I 2. Nucleotide excision repair 3. Base excision repair 4. Double-strand break repair What can happen if you can’t repair the mistake? Either cell death, suicide (apoptosis) or the DNA mutations can be passed on during replication. A. Germ cell: Genetically inherited mutation (not always bad) B. Somatic cell: Cancer DNA damage and replication mistakes and happen. What to do about it? Repair the mistakes
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Editing and correcting activities of DNA polymerase I DNA polymerase I replicates eukaryotic DNA The error rate during DNA replication is the spontaneous mutation rate (about 1 in 10 9 nucleotides) . This enzyme has a proofreading capability, where mismatched bases are excised and corrected Fig. 13-16, p. 545 However, some mistakes can get through
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A pyrimidine dimer can form within a DNA duplex following UV irradiation This is an example of the kind of DNA damage your skin gets in the sun This can also be caused by Ionizing radiation, common chemicals and thermal energy Luckily, our cells have a number of mechanisms to repair this kind of genetic damage Fig. 13-25, p. 553
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