DNA microarray: Difference between revisions

Revision as of 21:30, 26 April 2004

Revision as of 04:08, 18 May 2004

Line 3:

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, plasmids, 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.

Line 15:

Depending on the technology used to fabricate the chips, microarrays may also be used in identifying hereditary genetic mutations and variation in individuals and across populations. Generally termed "genotyping" applications, chips may be used in this fashion for forensic applications, rapidly discovering or measuring genetic predisposition to disease, and identifying DNA-based drug candidates.

The lack of standardization in non-commercial arrays presents an [[interoperability problem]] in [[bioinformatics]], which hinders the exchange of array data. Many researchers use Affymetrix technology to a large extent because it is popular and standardized. At the same time, various grass-roots [[open source|open-source]] projects are attempting to facilitate the exchange and analysis of data produced with non-proprietary chips. The MIAME standard for describing a microarray experiment is being adopted by many [[Scientific journal|journals]] as a requirement for the submission of papers based on microarray results.

==External links==