Contents 1 Why normalization ? 12 Introduction 13 Microarray Data Normalization : A Problem Formulation 24
نویسندگان
چکیده
The recent development of complementary DNA microarray technology provides a powerful analytical tool for genetic research. This tool allows one to study expression levels in parallel which represents an enormous gain in terms of experimental time invested. But always while carrying out comparisons of expression data using measurements from a single array or multiple arrays, the question of normalizing data arises. An essential answer is needed to be established to the following question: Does the variation in the intensity data represent true variation in the expression level of the genes present in the analysis or is this variation the result of experimental variability? If the problem addressed by this question is not resolved, any further type of data mining process on the data is worthless. The role of normalization is to separate true variation in expression values from di erences due to experimental variability. As mentioned before the microarray technology is a powerful tool that permits to study the expression level of thousands of genes at the same time, but usually in an experiment involving thousands of genes there are only few genes that are really of interest, those genes that overexpress as a \response"to the experiment practiced. Therefore it is useful to develop a method that will provide statistical information about these genes avoiding the processing of the data on the whole set of genes. In this technical memo it is proposed a new normalization method and error analysis that ultimately will provide the scientist with a statistical tool that wil allow to focus on a considerably reduced subset of genes from an originally much larger dataset. The usefullness of this type of reduction is justi ed under the scope of further analysis as for instance subsequent clustering techniques applied over the reduced data set. i
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تاریخ انتشار 2006