Microarray technology evolved from southern blotting, where fragmented DNA is attached to a substrate and them probed with a known gene or fragment.the use of a collection of distinct DNA's is array for expression profiling was first described in 1987,and the arrayed DNA were used to identify genes whose expression is modulated by interferon.
There early gene array were made by spotting cDNA onto filter paper with a pin-spotting device.the use of miniaturized microbarrays for gene expression profiling was first reported in 1955 and a complete eukaryotic genome 'saccharomyces cerevisiae' on a microarray was published in 1977.
A DNA microarray is a multiplex technology used in molecular biology and in medicine.it consists of an arrayed series of thousand of microscopic spots of DNA sequencs.this can be a short section of a gene or other DNA element that are used as probes to hybridize a cDNA or cRNA sample(called target) under high-stringency conditions.probe-target hybridization is usually detected and quantified by detection of fluorophoqe-silver or chemiluminescence-labelled targets to determinne relative abundance of nucleic acid sequence in the target.
In standard microarrays,the probe are attached to a solid surface by a covalent bond to a chemical matrix (via epoxy-silane,amino-silane).the solid surface can be glass or a silicon chip.they are commo known as gene chip or colloquially affy chip.other microarray platforms,such as illumina,use microscopic beads,instead of large solid support.DNA arrays a different from other types of microarray only in that they either measure DNA or use DNA as part of its detection system.
DNA microarray can be used to measure changes in expression levels,to detect single nucleotide polymorphism in genotyping or in resequencing mutant genomes.microarray also differs in fabrication,workins,accuracy,efficiency and cost.additional factors for microarray experiments are the experimental designs and the methods of analyzing the data.
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