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19 Cards in this Set
- Front
- Back
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Linkage phase
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Arrangement of alleles on each chromosome
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What is the linkage of two loci that are 50cM apart?
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They are unlinked
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What are the characteristics of markers?
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1. Highly polymorphic, 2. scattered throughout the genome, 3. easy to screen
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What is linkage analysis
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Determines what genes may be inherited together
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What does mapping by recombination depend on?
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Linkage depends on chromosomal location - distance between genes determines chance of cross over. Larger distance = higher chance of crossing over. Smaller distance = lower chance to cross over (ie linked)
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What is a centimorgan?
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Distance measured between two linked genes, 1% recombination rate
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LOD score
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Logarithm of odds -> likelihood ratio (odds that the genes are linked)
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What value LOD score is significant for linkage? No linkage?
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>3 = significant for linkage, < -2 = -2 no linkage
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What are the characteristics of markers for gene mapping?
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1. Highly polymorphic, 2. scattered throughout the genome, 3. easy to screen
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What is the difference between uninformative mating vs informative mating
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Informative matings have associated marker w/the disease. Uninformative matings have markers that tell you its associated sometimes and sometimes not associated
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How long do alleles stay linked?
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Recombination will slowly separate mutation from linked markers(over generations)
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Linkage disequilibrium
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Mutation and specific linked alleles inherited together(much more liekly person w/mutant gene carries a specific allele at linked marker)(ie hemochromatosis + HLA-A3) -> BUT OVER TIME recombination will separate mutation from marker
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Define: association
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Genetic association applies when linkage is not known or may not be a factor ->some specific allele significantly increases risk of a person being affected(ie ankylosing spondyliits + HLA-B27)
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What is the function of genome wide association studies?
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GWAS - used to locate genes(use microarrays w/SNP)
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Chromosome anomalies
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Translocation break points may be in a specific gene
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DNA libraries
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Library of DNA clones + human DNA + vector
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Define: candidate genes
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DNA sequences that may be reponsible for a given trait
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How do u figure out candidate genes?
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Positional -location is known, entire region sequenced, identify likely gene sequences, Functional - know likely function and chromosome, look for gene which fit both(ie collagen gene in marfans but its actually fibrillin gene)
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"electing" a candidate gene
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Compare sequences of gene from normal and mutant individuals -> look for expression in appropriate tissues ->compare expression in mutant vs normal -> express the gene to determine the gene product and its function
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