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Gene by environment effects
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Elevated Plus Maze (anxiety)
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Modelling E, G and GxE H 1 : phenotype ~ covariate H 2 : phenotype ~ covariate + LocusX H 3 : phenotype ~ covariate + LocusX + covariate:LocusX H 0 : phenotype ~ 1
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PRACTICAL: Inclusion of gender effects in a genome scan To start: 1. Copy the folder faculty\valdar\FridayAnimalModelsPractical to your own directory. 2. Start R 3. File -> Change Dir… and change directory to your FridayAnimalModelsPractical directory 4. Open Firefox, then File -> Open File, and open “gxe.R” in the FridayAnimalModelsPractical directory
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H 0 : phenotype ~ sex H 1 : phenotype ~ sex + marker
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scan.markers(Phenotype ~ Sex + MARKER, h0 = Phenotype ~ Sex,... etc) H 0 : phenotype ~ sex H 1 : phenotype ~ sex + marker
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scan.markers(Phenotype ~ Sex + MARKER, h0 = Phenotype ~ Sex,... etc) H 0 : phenotype ~ sex H 1 : phenotype ~ sex + marker
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scan.markers(Phenotype ~ Sex + MARKER, h0 = Phenotype ~ Sex,... etc) H 0 : phenotype ~ sex H 1 : phenotype ~ sex + marker
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head(ped.gender0) anova(lm(Phenotype ~ Sex + m1 + Sex:m1, data=ped.gender0)) head(ped.gender1) anova(lm(Phenotype ~ Sex + m1 + Sex:m1, data=ped.gender1)
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New approaches Advanced intercross lines Genetically heterogeneous stocks
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F2 Intercross x Avg. Distance Between Recombinations F1 F2 F2 intercross ~30 cM
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Advanced intercross lines (AILs) F0 F1 F2 F3 F4
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Chromosome scan for F12 position along whole chromosome (Mb) goodness of fit (logP) 0 100cM significance threshold QTL Typical chromosome
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PRACTICAL: AILs To start: 1. Open Firefox, then File -> Open File, and open “ail_and_ghosts.R” in the FridayAnimalModelsPractical directory
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Genetically Heterogeneous Mice
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F2 Intercross x Avg. Distance Between Recombinations F1 F2 F2 intercross ~30 cM
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Pseudo-random mating for 50 generations Heterogeneous Stock F2 Intercross x Avg. Distance Between Recombinations: F1 F2 HS ~2 cM F2 intercross ~30 cM
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Pseudo-random mating for 50 generations Heterogeneous Stock F2 Intercross x Avg. Distance Between Recombinations: F1 F2 HS ~2 cM F2 intercross ~30 cM
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Genome scans with single marker association
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High resolution mapping
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Relation Between Marker and Genetic Effect Observable effect QTL Marker 1
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Relation Between Marker and Genetic Effect Observable effect QTL Marker 2 Marker 1
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Relation Between Marker and Genetic Effect No effect observable Observable effect QTL Marker 2 Marker 1
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Hidden Chromosome Structure Observed chromosome structure Multipoint method (HAPPY) calculates the probability that an allele descends from a founder using multiple markers
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Haplotype reconstruction using HAPPY chromosome genotypes haplotype proportions predicted by HAPPY
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HAPPY model for additive effects
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Genome scans with single marker association
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Genome scans with HAPPY
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Results for our HS
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Many peaks mean red cell volume
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How to select peaks: a simulated example
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Simulate 7 x 5% QTLs (ie, 35% genetic effect) + 20% shared environment effect + 45% noise = 100% variance
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Simulated example: 1D scan
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Peaks from 1D scan phenotype ~ covariates + ?
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1D scan: condition on 1 peak phenotype ~ covariates + peak 1 + ?
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1D scan: condition on 2 peaks phenotype ~ covariates + peak 1 + peak 2 + ?
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1D scan: condition on 3 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + ?
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1D scan: condition on 4 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + ?
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1D scan: condition on 5 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + ?
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1D scan: condition on 6 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + ?
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1D scan: condition on 7 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + peak 7 + ?
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1D scan: condition on 8 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + peak 7 + peak 8 + ?
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1D scan: condition on 9 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + peak 7 + peak 8 + peak 9 + ?
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1D scan: condition on 10 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + peak 7 + peak 8 + peak 9 + peak 10 + ?
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1D scan: condition on 11 peaks phenotype ~ covariates + peak 1 + peak 2 + peak 3 + peak 4 + peak 5 + peak 6 + peak 7 + peak 8 + peak 9 + peak 10 + peak 11 + ?
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Peaks chosen by forward selection
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Bootstrap sampling 1 2 3 4 5 6 7 8 9 10 10 subjects
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Bootstrap sampling 1 2 3 4 5 6 7 8 9 10 1 2 2 3 5 5 6 7 7 9 10 subjects sample with replacement bootstrap sample from 10 subjects
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Forward selection on a bootstrap sample
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Bootstrap evidence mounts up…
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In 1000 bootstraps… Bootstrap Posterior Probability (BPP)
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Results
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Tea Break
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Study design 2,000 mice 15,000 diallelic markers More than 100 phenotypes each mouse subject to a battery of tests spread over weeks 5-9 of the animal’s life
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101 Phenotypes Anxiety (conditioned and unconditioned tasks) [24] Asthma (plethysmography) [13] Biochemistry [15] Diabetes (glucose tolerance test) [16] Haematology [15] Immunology [9] Weight/size related [8] Wound Healing [1]
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High throughput phenotyping facility
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Photo ID
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Open Field
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Anxious mouse Non anxious mouse
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Elevated Plus Maze (anxiety)
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Food hyponeophagia (reluctance to try new food)
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“Home Cage” activity
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Startle & Conditioning
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Plethysmograph
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Glucose Tolerance Test (diabetes)
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Wound healing
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PRACTICAL: http://gscan.well.ox.ac.uk
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END
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An individual’s phenotype follows a mixture of normal distributions
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m Maternal chromosome Paternal chromosome
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m Chromosome 1 Chromosome 2 ABCDEFABCDEF Strains
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Markers m ABCDEFABCDEF Strains
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Markers m ABCDEFABCDEF Strains
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Markers m 0.5 cM
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Markers m 0.5 cM 1 cM
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Markers m 0.5 cM 1 cM
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Analysis Probabilistic Ancestral Haplotype Reconstruction (descent mapping): implemented in HAPPY http://www.well.ox.ac.uk/~rmott/happy.html
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M1 Q M2 m1 q m2 M1 ? m2 recombination
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M1 Q M2 m1 q m2 m1 Q M2 M1 q m2 M1 q m2
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M1 Q M2 m1 q m2 M1 Q m2 M1 Q m2 m1 q M2 m1 Q M2 M1 q m2 M1 q m2
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M1 Q M2 m1 q m2 M1 m2 M1 m2 m1 m2 m1 M2 M1 m2 M1 m2 Qq Qqq Q
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M1 ? m2 m1 ? m2 cM distances determine probabilities
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M1 ? m2 m1 ? m2 cM distances determine probabilities Eg,
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Interval mapping M1 M2 m1 m2 M1 m1 M2 m2 LOD score
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Interval mapping M1 M2 m1 m2 M1 m1 M2 m2 LOD score Q q
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Interval mapping M1 M2 m1 m2 M1 m1 M2 m2 LOD score Q q
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Interval mapping M1 M2 m1 m2 M1 m1 M2 m2 LOD score Q q
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