DAKL7-032410DNARepair

DAKL7-032410DNARepair - DNARepair Our current understanding...

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DNA Repair Image: http://www.wsu.edu/~smerdon/ “Our current understanding is that DNA is the only molecule that organisms repair rather than replace.” – your book, pg.531
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Review of Last Lecture: Mutagenesis Mutations are the source of genetic diversity, but usually have a negative impact on gene function. Mutations can arise spontaneously , or by exposure to a mutagen Point mutations can be caused by rare nucleotide tautomers, direct damage to bases (cytosine deamination, oxidation, or an abasic site), or by insertion of a base analog. Insertions and Deletions can be caused by Intercalating Agents Many human diseases are caused by triplet repeat expansions . These can be caused by strand slippage during replication. Exposure to UV light can cause covalent linkages between adjacent T nucleotides on the same strand (Thymidine dimers)
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Learning Objectives for DNA Repair Mechanisms I. Direct repair I. Pre-replication mechanisms Nucleotide Excision Repair Bypass polymerase Base Excision Repair III. Post-replication mechanisms Cell-cycle checkpoints and apoptosis Mismatch repair Double-strand break repair IV. DSB repair in non-dividing cells
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Pre-replication vs Post-replication repair: Mutations are NOT “fixed” (permanent) until replication
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DNA Repair Mechanisms I. Direct repair I. Pre-replication mechanisms Nucleotide Excision Repair Bypass polymerase Base Excision Repair III. Post-replication mechanisms Cell-cycle checkpoints and apoptosis Mismatch repair Double-strand break repair IV. DSB repair in non-dividing cells
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Direct repair: Photolyase uses light energy to repair UV damage Fig 15-22 Photolyase binds to the photodimer and splits it to regenerate the original bases = Direct reversal of damaged DNA
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DNA Repair Mechanisms I. Direct repair I. Pre-replication mechanisms Nucleotide Excision Repair Bypass polymerase Base Excision Repair III. Post-replication mechanisms Cell-cycle checkpoints and apoptosis Mismatch repair Double-strand break repair IV. DSB repair in non-dividing cells
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