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[[File:From_spit_to_DNA-sample.webm|thumb|''How to use a microarray for genotyping.'' The video shows the process of extracting genotypes from a human spit sample using microarrays. Genotyping is a major use of DNA microarrays, but with some modifications they can also be used for other purposes such as measurement of gene expression and epigenetic markers.]]
A '''DNA microarray''' (also commonly known as [[DNA]] chip or [[biochip]]) is a collection of microscopic DNA spots attached to a solid surface. Scientists use DNA [[microarray]]s to measure the [[Gene expression|expression]] levels of large numbers of genes simultaneously or to [[genotyping|genotype]] multiple regions of a genome. Each DNA spot contains [[Pico-|picomoles]] (10<sup>−12</sup> [[Mole (unit)|moles]]) of a specific DNA sequence, known as ''[[Hybridization probe|probe]]s'' (or ''reporters'' or ''[[oligonucleotide|oligo]]s''). These can be a short section of a [[gene]] or other DNA element that are used to [[Nucleic acid hybridization#Hybridization|hybridize]] a [[cDNA]] or cRNA (also called anti-sense RNA) <!--Agilent kit--> sample (called ''target'') under high-stringency conditions. Probe-target hybridization is usually detected and quantified by detection of [[fluorophore]]-, silver-, or [[chemiluminescence]]-labeled targets to determine relative abundance of nucleic acid sequences in the target. The original nucleic acid arrays were macro arrays approximately 9 cm × 12 cm and the first computerized image based analysis was published in 1981.<ref name="Taub">{{cite journal|last1=Taub|first1=Floyd|title=Laboratory methods: Sequential comparative hybridizations analyzed by computerized image processing can identify and quantitate regulated RNAs|journal=DNA|date=1983|volume=2|issue=4|pages=309–327|doi=10.1089/dna.1983.2.309|pmid=6198132}}</ref> It was invented by [[Patrick O. Brown]]. An example of its application is in SNPs arrays for polymorphisms in cardiovascular diseases, cancer, pathogens and GWAS analysis.
== Principle ==
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