A technique which allows the analysis of gene expression or gene structure in hundreds to thousands of genes simultaneously by measuring the extent of nucleic acid hybridization (q.v.) in DNA microarrays. DNA microarrays are small glass microscope slides, silicone chips, or specialized membranes containing hundreds or thousands of closely spaced spots, to each of which are bound short, single-stranded gene sequences. The DNA for the arrays is derived either from genomic DNA or cDNA (q.v.) and applied with a robotic instrument. Expression of genes represented on a DNA microarray can be assayed by hybridization with fluorescently- or radioactively- labeled cDNA (q.v.) or mRNA (q.v.) probes (q.v.) and quantitative analysis of the extent of nucleic acid hybridization (i.e., fluorescence or radioactivity) on each spot on the microarray. This approach can be used to identify transcribed regions in a genome (q.v.). By simultaneous hybridization with different-colored fluorescent probes derived from different sources, one can compare gene expression in different cell types, examine temporal and spatial expression patterns, or identify genetic variations associated with disease. In an alternative approach, the DNA for the microarray is synthesized directly on the microarray support, using as templates (q.v.) single-stranded oligonucleotides (q.v.) which have been annealed to the support and which are derived from individual genes. Hybridization of oligonucleotide arrays (often called DNA chips) with genomic DNA probes can detect mutations or polymorphisms in gene sequences. A helpful Web site for microarray users is www.biochipnet.de. One of the earliest studies utilizing this technology involved Arabidopsis (q.v.). The differential expression of 45 genes was measured with a microarray of 45 cDNAs. See Chronology, 1995, Schena et al.; 1999, Evans and Wheeler.
Subjects: Genetics and Genomics.