L22 Repair and recombination

L22 Repair and recombination - Repair and Recombination 1...

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Repair and Recombination 1
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Last Time What are mutations and how do they affect phenotype? Common mutations Causes of mutation Spontaneous and Induced 2
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Repair and recombination DNA repair systems Mismatch repair, Excision repair, Double strand break repair Homologous recombination - repair using a homologous chromosome Gene conversion resulting from homologous recombination Transposition - the jumping genes 3
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Xeroderma pigmentosa Genetic disorder in which one of the repair enzymes is mutated and nonfunctional Severe sensitivity to sun 4
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http://www.mainenterprises.co.nz/downloads/Sunbathing.jpg Thymine dimers: mutations caused by UV-light 5
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Nucleotide excision repair Thymine dimer distorts DNA Nuclease cuts out damaged DNA DNAP repair synthesis DNA ligase seals the backbone Repairs modifed bases, missing bases and crosslinks 6
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Mismatch repair Old New G A How does the cell determine which strand is the old (template) strand? 7
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S L H Mut S - S earches for mismatch Mut L - L inks MutS to MutH Mut H - H olds onto CH 3 -ed strand Mut U - U nwinds and separates strands (helicase) Exonuclease - chews back DNA DNAP synthesizes new strand Ligase seals backbone 8
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Breaks occur 10-100s times per day per cell!!
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This note was uploaded on 03/29/2009 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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L22 Repair and recombination - Repair and Recombination 1...

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