DNA array-based technologies are widely used in biological research, most commonly to measure differential gene expression--that is, comparing the relative levels of RNA transcripts in different cell or tissue samples.1,2 In a common scenario, researchers label cDNA targets prepared from control and experimental samples with two different fluorescent dyes. They then hybridize these two samples simultaneously to a single microarray bearing tens of thousands of oligonucleotide probes. Finally, the scientists detect those transcripts that differ in abundance in the control and experimental samples by quantifying the fluorescent signal intensities of each spot.

Investigators can either generate their own arrays in-house if they have the requisite instrumentation, or alternatively, custom-order them from companies that provide this service. However, growing numbers of "stock," premade arrays are becoming commercially available. Owing to their prefabricated nature, these products offer less flexibility in experimental design. However, purchasing arrays "off the shelf" may prove to...

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