Wright BIO 2110 - Rec10_cumulative distributions (7 pages)

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Rec10_cumulative distributions



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Rec10_cumulative distributions

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Pages:
7
School:
Wright State University
Course:
Bio 2110 - Principles of Molecular and Classical Genetics

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BIO 2110 Recitation 10 QTLs Kolmogorov Smirnov test 2 December 2016 Name Names of group members In QTL analyses genotypes are determined for multiple genetics markers usually SNP or microsatellite markers across the genome For each marker the population is divided by genotype Phenotypic distributions of these genotypes then are compared QTLs are identified mapped thorugh the identification of markers for which phenotypic distributions of different genotypes differ significantly Usually QTL data sets are quite large and analyses are done computationally However for small data sets and for instructors who think there is pedagogical value in it distributions can be compared by hand On the last page of this handout data for the fruit weights and genotypes of BC progeny are given Your task is to compare the weight distributions of B B and B S BC progeny for two of these markers your choice using the Kolmogorov Smirnov K S test In the K S test distributions first are converted into cumulative distributions see below From these cumulative distributions a D statistic the largest separation of the cumulative distributions is determined From this D statistic and the sample sized of each distribution a p value can be determined 1 000 0 800 0 600 BB 0 400 BS Cumulative Distributions that don t differ significantly 0 200 0 000 1 3 5 7 9 11 13 15 17 19 21 1 000 0 800 0 600 D stat 0 400 BB BS 0 200 0 000 1 3 5 7 9 11 13 15 17 19 21 Cumulative distributions that do differ significantly Directions For determine how many are B B homozygotes and how many are B S heterozygotes For each genotype list the number of individuals in each weight class Determine the cumulative distribution of phenotypes for each genotype Determine for each weight class what fraction of individuals weigh that much or less e g for the M1 marker there are eight B B homozygotes Three of these weigh 170 gm or less Therefore at 170 the value for the cumulative distribution is 3 8 or 0 375 It remains at 0 375 at 171 and 172 gm no additional B B homozygotes at these weights Four homozygotes weigh 173 gm or less So at 174 gm the cumulative distribution value is 4 8 or 0 500 By 185 gm the maximum weight recorded all cumulative distribution values for all genotypes at all markers should be equal to1 000 For each weight 165 185 determine the difference between the cumulative distributions for B B homozygotes and B S heterozygotes this is equal to the absolute value of B B minus B S e g for marker M1 at 171 gm this is equal to 0 375 0 417 0 0412 Identified the maximum difference between the B B and B S cumulative distributions This value diffmax is the D statistic go to https home ubalt edu ntsbarsh Business stat otherapplets pvalues htm rkstwo enter the D statistic the



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