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Compared to teosinte 38 of genes analyzed 23 the loci

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Unformatted text preview: ional reduction in Ne that are locus specific – for loci affecting the traits under artificial selection • Test: Look for genes that show evidence of a more severe bottleneck than is typical of the rest of the genome 30 “selection candidates” have deficit of polymorphism in maize compared to teosinte = 3.8% of genes analyzed 23 -The loci affecting traits that are under selection will experience the g reatest reduction in Ne during artificial selection -If we can find evidence of a more SEVERE bottleneck than is typical for t he rest of the genome, it indicates that our ancestors were imposing a rtificial selection that precipitated this bottleneck (like the red diagram) Neutral evolution with fit to bottleneck demographic scenario Wright et al. 2005 Science -On the X Axis: -Maize shows 0 polymorphism while t he Teo. ancestor shows variability -These loci are like the skinniest part o f the red diagram above - they e xperienced severe bottleneck -These simulated results c annot be accounted for by p urely random bottlenecks -Only artificial selection can e xplain the magnitude of the 4 b ottleneck 04/03/2013 Results for maize & teosinte Why do we care about genetic variation in crops? • 2% to 4% of the teosinte genome experienced strong artificial selection during domestication 1. Clues to past artificial selection – On what traits did our ancestors select? – Detectable imprint in the genome evident in population genetic patterns 2. Future improvement of crops • Extrapolated to genome: 1200 genes – Is it possible to keep breeding better crops without genetic engineering? – Or is there insufficient genetic variation? • Some genes expected: – Genes for ear production, growth, morphological traits Make corn grow tall & straight • Some genes unexpected: 3. Pest and pathogen management – Can we reduce crop loss to pests? – 5 of...
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