 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 microarrays to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome. each dna spot contains picomoles (10â12 moles) of a specific dna sequence, known as probes (or reporters or oligos). these can be a short section of a gene or other dna element that are used to hybridize a cdna or crna (also called anti-sense rna) 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 basic microarray== since an array can contain tens of thousands of probes, a microarray experiment can accomplish many genetic tests in parallel. therefore arrays have dramatically accelerated many types of investigation. in standard microarrays, the probes are synthesized and then attached via surface engineering to a solid surface by a covalent bond to a chemical matrix (via epoxy-silane, amino-silane, lysine, polyacrylamide or others). the solid surface can be glass or a silicon chip, in which case they are colloquially known as an affy chip when an affymetrix chip is used. other microarray platforms, such as illumina, use microscopic beads, instead of the large solid support. alternatively, microarrays can be constructed by the direct synthesis of oligonucleotide probes on solid surfaces. dna arrays are different from other types of microarray only in that they either measure dna or use dna as part of its detection system. dna microarrays can be used to measure changes in expression levels, to detect single nucleotide polymorphisms (snps), or to genotype or targeted resequencing (see uses and types section). microarrays also differ in fabrication, workings, accuracy, efficiency, and cost (see fabrication section). additional factors for microarray experiments are the experimental design and the methods of analyzing the data (see bioinformatics section). == history == microarray technology evolved from southern blotting, where fragmented dna is attached to a substrate and then probed with a known dna sequence.{{cite journal|journal=nucleic acids res.|date=11 apr 1992|volume=20|issue=7|pages=1679â84|title=oligonucleotide hybrid
Bioinformatics DNA Gene_expression Glass_coating_and_surface_modification Microarrays Microtechnology Molecular_biology_techniques