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Note7 - see the animations on the web site for help C...

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Lecture 8 MCB 161 S. Harmer 1/28/2010 DNA Repair, Recombination and Positional Cloning Reading Review Watson text, pp. 6 - 13; 283- 310; also see the link on the ‘assigned reading’ web page. Problems see the web site I. DNA repair mechanisms A. Chemically modified bases i. Direct repair of lesion (e.g. photolyase) ii. Excision repair (removal of one base or of stretch of nucleotides) B. Double strand breaks i. Non-homologous end joining ii. Homologous recombination – also essential for meiosis (and genetics!) II. Mechanism of homologous recombination A. Double Holliday junction model (aka double strand break repair model) B. Holliday junctions can be resolved in two ways; only one results in crossing over of the chromosome arms (and thus reassortment of genes flanking the original cleavage site ( NOTE
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Unformatted text preview: : see the animations on the web site for help!) C. Enzymology of HR: Chromosome alignment; Spo11 generates DSB; RecA/Rad51 performs homology search and catalyzes strand exchange III. Positional cloning - molecular identification of mutation underlying a phenotype A. Unlinked genes segregate independently (independent assortment) B. Genes located near each other on a chromosome tend to be inherited together (they are linked). Physical proximity means alleles seldom separated by recombination C. Linkage analysis is used to find the approximate location of a mutant gene; fine-scale mapping using molecular markers (like SSLPs) is then used to determine the precise location of the mutant gene D. Genes in the mutant interval are then sequenced to identify the responsible locus....
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