ABSTRACT
Spotted microarrays are now commonly used for analysis of gene expression levels and DNA copy numbers for a variety of clinical and laboratory investigations. The ability to simultaneously measure the several thousands of genetic transcript levels or changes in
DNA copy number affords the opportunity to characterize complex biological processes at a level of detail not previously feasible; see, for example,.1-5
A description of the cDNA microarray provides an example of the technological details. First cDNA is spotted on the microarrays using a print-tip, with typically 16 or 32 print-tips per array. Next mRNA from a sample of interest and a reference sample are reverse-transcribed into cDNA and are labeled differentially with two fluorescent dyes, for example Cy3 (green) and Cy5 (red). Two pools of cDNA are then mixed and washed over the array. The array is scanned for Cy3 and Cy5 fluorescent intensities, which reflect the relative amount of mRNA transcript for a given gene. The data consist of Cy3 and Cy5 measurements for every spot on every array, with each spot corresponding to transcripts, in the form of cDNA, encoded by a distinct gene.
