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Explore gene expression data for mouse dataset through preprocessing, normalization, and statistical testing using CyberT software. Utilize SNOMAD for array normalization and analyze condition effects. Visit provided links for tools and data sets.
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Expression profiling & functional genomicspreprocessingExercises
Exercises Array by array approach Log transformation Filtering Normalisation Ratio Test statistic (T-test)
CyberT • Use the normalized data to find statistically differentially expressed genes: CyberT software • oefnbaldi.xls • http://visitor.ics.uci.edu/genex/cybert/ The file contain the 4 normalised ratios (see SNOMAD) T test on the ratios Array 1 Per gene, per condition 4 measurements available Paired samples Array 2
Exercises • Dataset: mouse dataset • cDNA experiment:SNOMADtest2.txt • Analyze array1 by SNOMAD • Array by array normalization • ONE:measurements of the red channel • TWO: measurements of the green channel http://pevsnerlab.kennedykrieger.org/snomadinput.html http://www.bio.davidson.edu/courses/genomics/chip/chip.html
SNOMAD http://pevsnerlab.kennedykrieger.org/snomadinput.html
SNOMAD Results • Untransformed data • Note the multiplicative error • Note the influence of the Dye and condition effects
SNOMAD Results • Linear normalisation of the untransformed data • Multiplicative effects still existing (not common) • Data after log transformation • Note the removal of the multiplicative error • Note the effect of the Dye and Condition • Note the non linear character of the data
SNOMAD Results M/A plot M/A prior to normalisation
SNOMAD Results Non linear lowess fit M/A after normalisation
SNOMAD Results Original data Log transformed data Untransformed log ratio (M) Mean log intensity (A) Linearized log ratio CyberT