Genome 371 Lecture 16 - Genome 371 Lecture 16 4:17 PM Home...

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1/26/11 4:17 PM Genome 371 Lecture 16 Page 1 of 12 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_16.html Lecture 16 Mapping genes in humans-3 29 Nov 2010 Lecture 16 handout (pdf) Subscribe to podcast: Slide 1 Slide 2 Home Course mechanics Help hours Calendar Syllabus Lectures, Podcasts Quiz Sections Practice problems Exams GoPost Send email to class Useful links The Gradiator
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1/26/11 4:17 PM Genome 371 Lecture 16 Page 2 of 12 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_16.html Slide 3 Slides 4 and 5 (From end of Lecture 15 handout) The premise is that at the moment a disease- causing allele arises due to mutation on some chromosome, that allele is in association with the particular SNP alleles of the SNPs along that chromosome -- i.e., the disease-causing mutation is in association with the alleles of the haplotype making up that chromosome. Over subsequent generations, the association is broken down into smaller blocks so that eventually the disease- causing allele remains associated only with the SNP alleles in its immediate vicinity. We can use this idea to find where in the genome the disease- causing allele (and therefore, the gene) is located, by searching for SNP alleles that are associated with the disease phenotype -- i.e., SNP alleles that co-occur with the disease phenotype more often than would be expected by chance. Note that the SNPs are all common SNPs -- i.e., they are locations where there is polymorphism in the general population, and the SNPs we are scanning are present in all populations. These SNP alleles may not themselves be causing the disease; it's just that we are trying detect the remnants of the original "neighborhood" of the disease-causing allele. Slide 6 FYI: In the early days of whole-genome association mapping, the technology was not well developed, the density of known polymorphisms was low, and the necessary statistical tests had not been fully developed. As a result, many disease genes that were originally claimed as having been mapped by whole-genome association turned out not to hae been mapped correctly. In the last few years, however, the situation has turned around. .. at current count, genes contributing to some 300+ disorders have been mapped this way, and the rate of discovery is still increasing. A particularly powerful outcome of this approach is that if multiple genes are contributing to the phenotype, this approach (if used correctly) can pinpoint multiple regions of the genome to examine -- i.e., we would see
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1/26/11 4:17 PM Genome 371 Lecture 16 Page 3 of 12 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_16.html haplotypes in common between "cases" vs. controls for multiple regions in the genome.
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Genome 371 Lecture 16 - Genome 371 Lecture 16 4:17 PM Home...

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