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Chapter 15: Non-Mendelian Genetics (sex and gene linkage)

Chapter 15: Non-Mendelian Genetics (sex and gene linkage). Timeline of Events. Mitosis 1875 Meiosis 1890s Chromosomes being the “inheritance factors” that Mendel referred to 1902. Linked genes. Genes that often travel together during meiosis and because they are on the same chromosome

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Chapter 15: Non-Mendelian Genetics (sex and gene linkage)

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  1. Chapter 15: Non-Mendelian Genetics (sex and gene linkage)

  2. Timeline of Events • Mitosis 1875 • Meiosis 1890s • Chromosomes being the “inheritance factors” that Mendel referred to 1902

  3. Linked genes • Genes that often travel together during meiosis and because they are on the same chromosome • Why some traits are often seen together… http://www.youtube.com/watch?v=-_UcDhzjOio

  4. Genetic Maps & Map Units • By knowing recombination frequencies you can determine the approx. distance between genes on the same chromosome in map units • If you know the map units of traits on a chromosome you can create a genetic map (shows the order in which the genes appear on a chromosome NOT the exact distances apart the loci of the genes are)

  5. Figuring out the # of map units apart genes are… • Snapdragons with genotypes CCDD and ccdd are crossed. The CcDd progeny were then crossed with ccdd plants and we obtain  30% CcDd,  20% ccD 20% Ccdd and  30% ccddoffspring. We conclude: A. Genes C and D are linked, separated by 20 map units B. Genes C and D are linked, separated by 30 map units C. Genes C and D are linked, separated by 40 map units D. Genes C and D are unlinked

  6. Figuring out the # of map units apart genes are… • Snapdragons with genotypes CCDD and ccdd are crossed. The CcDd progeny were then crossed with ccdd plants and we obtain  30% CcDd,  20% ccD 20% Ccdd and  30% ccddoffspring. We conclude: A. Genes C and D are linked, separated by 20 map units B. Genes C and D are linked, separated by 30 map units C. Genes C and D are linked, separated by 40 map units (CORRECT 1% = 1 map unit, therefore 40% recombinants = 40 map units) D. Genes C and D are unlinked

  7. Try it… • Snapdragons with genotypes DDEE and ddee are crossed. The DdEe progeny are then crossed with ddee plants and we obtain 45% DdEe, 5 % ddEe, 5% Ddee and 45% ddee. How  far apart are genes D and E? a.      5 map units b.      10 map units c.      45 map units d.      Genes D and E are not linked

  8. Try it… • Snapdragons with genotypes DDEE and ddee are crossed. The DdEe progeny are then crossed with ddee plants and we obtain 45% DdEe, 5 % ddEe, 5% Ddee and 45% ddee. How  far apart are genes D and E? a.      5 map unitsb.      10 map units (COREECT 1% = 1 map unit, therefore 10% recombinants = 10 map units) c.      45 map units d.      Genes D and E are not linked

  9. Practice problems • Pg 291-292 #s: 4, 5, 8, 9, 13

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