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Linkage analysis and genetic mapping

Linkage analysis and genetic mapping. Marker assisted selection and “map-based” breeding “Mendelizing” QTL. “Mendelizing QTL”. We can more completely characterize quantitative traits and the loci that confer quantitative inheritance Identify the number of loci conferring a Quant. Trait

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Linkage analysis and genetic mapping

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  1. Linkage analysis and genetic mapping • Marker assisted selection and “map-based” breeding • “Mendelizing” QTL

  2. “Mendelizing QTL”

  3. We can more completely characterize quantitative traits and the loci that confer quantitative inheritance • Identify the number of loci conferring a Quant. Trait • Identify gene action and estimate the magnitude of individual loci (VQTL/Vp) • Select for genotype when phenotypic selection is less efficient

  4. New technology opens the possibility of “map-based” breeding. How easy will it be to pyramid genes or break unfavorable linkage?

  5. Synthesize information from numerous crosses to understand patterns of genome organization • Clusters of disease resistance genes • Candidate genes for Quant. Trait loci

  6. Power of modern genetic mapping in breeding applications comes from: • Combining classical and new techniques • Placing “economic traits” onto maps • Working in genetic backgrounds that favor application

  7. Building Genetic Maps • Single-locus analysis • Two-locus analysis • Measuring linkage distance • Linkage grouping • Gene ordering • Multi-point analysis

  8. Building Genetic Maps • Single-locus analysis • Two-locus analysis • Measuring linkage distance • Linkage grouping • Gene ordering • Multi-point analysis

  9. Definition of Genetic Linkage • The association of genes located on the same chromosome • The association or non-independence among alleles at more than one locus • Statistical definition

  10. Linkage between qualitative traits • Does each locus segregate as expected? • Mendel’s first law • Do the loci assort independently? • Mendel’s second law • What is the distance between loci?

  11. Estimation of linkage distance • Historical overview • Additive method • Weighted mean method • Product method • Maximum likelihood • Log of the odds

  12. Keep in mind the following: • We are first going to cover the theory and practice of linkage analysis • Application of linkage data and “map-based” breeding are up to the creativity of the breeder • There are sometimes conflicting goals between breeding applications and genetic applications

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