DNA microarray: Difference between revisions

Revision as of 12:26, 16 July 2004

Revision as of 12:29, 16 July 2004

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Machines use such chips to screen a biological sample for the presence of many [[genetic sequence]]s at once. The affixed DNA segments are known as ''probes.'' Hundreds of identical probes are affixed at each point in the array to make the chips effective detectors.

Although the name "GeneChip" is a trademark of [[Affymetrix]], microarray users generally use this term to refer to any microarray, not just those sold from a company. While Affymetrix arrays are limited to featuring small oligonucleotides of less than 25 bases, many microarrays consist of [[PCR]] products, genomic DNA, BACS[[BAC]]s, plasmids[[plasmid]]s, or long oligos (70 bases). Microarrays may be made by any number of technologies, including simple printing onto glass slides. Microarrays for expression profiling was first published in 1995 (Science) and the first complete eukaryotic genome (Saccharomyces cerevisiae) on a microarray was published in 1997 (Science).

Typically arrays are used to detect the presence of [[mRNA]]s that may have been [[transcription|transcribed]] from different genes and which encode different proteins. The RNA is extracted from many cells of a single type, then converted to cDNA and "amplified" in [[concentration]] by [[RT-PCR|rtPCR]]. [[Fluorescent tag]]s are chemically attached to the strands of DNA. A cDNA [[molecule]] that contains a sequence complementary to one of the single-stranded probe sequences will stick via ''base pairing'' (more at [[DNA]]) to the spot at which the complementary probes are affixed. The spot will then [[fluorescence|fluoresce]] (or glow) when examined.