A '''gene chip''' is a piece of glass or plastic on which pieces of [[DNA]], which are referred to as "probe sequences," have been affixed in a microscopic array. Machines use such chips to simultaneously screen a single biological sample for the presense of many [[genetic sequence]]s.
Because '''"GeneChip"''' is a trademarked name owned by [[Affymetrix]], scientists tend to speak and write about "gene chips" only in reference to the chips that Affymetrix makes. Brought to market in [[1996]], these were the first to come into use, and they are referred to generically as '''oligonucleotide arrays,''' because the probe sequences are short pieces of DNA about 10 to 50 [[nucleotide]]s long. A relatedstill broader term is '''microarray''', which refers not only to aGeneChips chipbut to chips that usesuse much longer probe sequences, (typicallysuch wholeas the entire [[cDNAgene]]s) that havemay beenbe affixedcontained inon [[cDNA]]s. Because, Affymetrix owns a waypatent thatboth differson fromthe use of oligonucleotides probes as well as on the patentedmeans techniquethe Affymetrixcompany uses to makeaffix GeneChipsthem to the chip, microarrays that are not made by Affymetrix are manufactured by a different technique that is non-proprietary.
GeneUsing chips are covered with gridlike patterns of short [[DNA]] strandsmicroarrays, called probes. Each probe can specifically bind to a different gene sequence. When sample DNA is placed on the chip, researchers can study which probes bind DNA from the sample to determine which genes were present in the sample. Genes from cancerous cells can be analyzed with gene chips to discover which genes are present in the cancerous cells that are not present in healthy cells. Cells can be treated with drugs, and the gene chip can analyze those genes to determine which genes are turned on or off by the drug.
Since there are hundreds of thousands of probes on a gene chip, using a gene chip can be the equivalent of thousands of conventional genetic tests. Gene chips have therefore dramatically accelerated the pace of genetic research.
