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DNA - Repair Mechanism Lesion Bypass When does it happen...

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Repair Mechanism When does it happen? How does it work? What is the outcome? Lesion Bypass During replication- have to keep going! WIll replicate through Thymine dimer Switches normal Pol for special Pols that can blow through the damage. Are good at recognizing Tdimer Often causes mutation-- but lets cell live (replication doesn t stall) Direct Reversal When bases are chemically damaged (thymine dimer, methylation damage) Photoreactivation: reverses Tdimer with visible light. Methyltransferase: reverse met damage No mutations-- just reverses base damage Damage Removal: When you need to correct mistakes the Pol made or DNA damage Excise damaged area and repolymerize fresh DNA Generally corrects damage, no mutations (excepting ds Break repair non-homologous) 1. Base excision repair Single base is damaged or converted to U 1-2 base removed then residue removed, polymerase adds new NTP Corrects damage, no mutation-- uses other un-damaged strand as template 2. Mismatch excision repair Proofreading after
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