1-27-11 DNA Repair-Homologous Recombination

1-27-11 DNA Repair-Homologous Recombination - Review -...

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1 Review - Group Work 1: What parts of a person's body should be most carefully protected from ultraviolet radiation? Why? Skin and eyes What parts of a person's body should be most carefully protected from gamma or X-rays? Why? The vital internal organs, and gonads When during a person's life would it be most important to avoid exposure to mutagens? Why? 1. Pregnancy - especially early embryonic develoment; 2. Early childhood - the growth years 3. Young adulthood, i.e., the reproductive years Group work 2 : 1. Which repair pathway would most probably repair the following DNA lesions: a.Oxidative damage to bases from oxygen free radicals? b.Mis-incorporation of one nucleotide caused by tautomeric shift occurring just before replication? c. A thymine dimer in a gene expressed in skin cells? January 27, 2011 DNA Double-Strand Break Repair and Homologous Recombination Next week's reading: Watson, Chapter 10 See also the textbook website (sixth edition) or interactive CD-ROM (fifth edition). Please look at the two animations for Chapter 10, on "The Holliday Model" and "Homologous Recombination".
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2 Nucleotide Excision Repair (NER) Base Excision Repair (BER) Mismatch Repair (MMR) To recap: much DNA damage affects only one strand. .. Excision. .. Pol …templated resynthesis. .. …and ligation. …and can be repaired with perfect Fdelity: But what about lesions that affect both strands, i.e., double-strand breaks ? A severe lesion - hard to repair, and very dangerous to the cell: • No intact opposite strand available as template. • Failure to repair means loss of part (or all) of a chromosome arm - potentially hundreds of genes. • Mis-repair can result in chromosomal rearrangements, e.g., large deletions, inversions, translocations. Two major pathways of DSB repair : NHEJ Non-Homologous End Joining: • Uses no template. • Often produces sequence changes at the repair junction. • Can result in translocation, if ends from two different chromosomes get joined. It’s mutagenic, so why would cells do this kind of repair? HRR
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This note was uploaded on 04/04/2011 for the course GENETICS 385 taught by Professor Brennemanandgordon during the Spring '11 term at Rutgers.

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1-27-11 DNA Repair-Homologous Recombination - Review -...

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