Genome 371 Lecture 13 - Genome 371 Lecture 13 1/26/11 4:17...

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1/26/11 4:17 PM Genome 371 Lecture 13 Page 1 of 13 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_13.html Lecture 13 Mapping genes: Molecular markers 15 Nov 2010 Lecture 13 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 13 Page 2 of 13 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_13.html Slide 3 Slide 4 Slide 5 Slide 6
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1/26/11 4:17 PM Genome 371 Lecture 13 Page 3 of 13 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_13.html Slide 7 Slide 8 Slide 9 To emphasize: the DNA sequence variants here may not be in a gene (in fact, most such locations will not be in genes) -- but that's okay, as long as we know the location of that variation site in the genome. If we know the location, and we know that there is a potential for heterozygosity at that locus, we can test for linkage between that locus and any other locus (e.g., an unknown gene, or in the case of humans, an disease gene of unknown sequence).
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1/26/11 4:17 PM Genome 371 Lecture 13 Page 4 of 13 http://courses.washington.edu/au371mkr/resources/lecture_notes/lecture_13.html Slide 10 Goal: we want to find the location of some gene in the genome; we want to know where it is along the genomic DNA. In this example, we are trying to locate an eye color gene. Strategy: Look for linkage between the eye color gene and known DNA markers (in real life we would have to do trial and error with many different markers to find one that showed linkage to our gene of interest). These DNA markers don't have to code for anything; they are just DNA alleles at known locations in the genome, so they serve as genomic landmarks. To find the DNA marker genotype of any individual, we'd have to do a DNA test (e.g., sequence a portion of the genome) for that individual. Slide 11 Just as with any other linkage test, we set up a cross between a heterozygote and a testcross parent. What's different here is that one of the loci is a DNA marker (and therefore there isn't a "recessive" allele for that locus); the principle, however, is exactly the same: the heterozygous parent can make 4 gamete genotypes; if the two loci are unlinked, the four gamete types should be made in equal proportions, whereas if they are linked, the proportions will be skewed in favor of the parental type genotypes. Fruit flies being diploid organisms, the gamete genotypes are detected based on the progeny they create. Slide 12 Slide 13 Note that the testcross parent need not actually be homozygous for the DNA marker -- I made the male fly homozygous for the DNA marker just for the sake of simplicity. In reality, because the DNA test will reveal both alleles, the testcross parent need not be homozygous for the DNA marker-- BUT, for the cross to be useful, the genotype has to be such that you can unambiguously tell
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Genome 371 Lecture 13 - Genome 371 Lecture 13 1/26/11 4:17...

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