DNA microarray

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DNA microarray

An orderly arrangement of DNA sequences on a small solid support, usually a membrane or glass slide, used to quickly survey the simultaneous expression of many genes. Also called DNA chip.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
An array of DNA oligonucleotides synthesised in situ by photomasking on a semiconductor chip
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

DNA mic·ro·ar·ray

A technique used to identify the entire gene expression of bacterial cells. Microscopic spots of DNA are placed on a solid support in an array, and unknown samples fluorescently labeled are hybridized to the DNA on the array. A scanner is used to identify hybrids.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

DNA microarray

A collection of tens of thousands of DNA single-strand molecular probes capable of detecting specific genes or measuring gene expression in a sample of tissue. A gene is expressed when it is transcribed into messenger RNA (mRNA) and forms a protein. Currently, DNA microarrays are mainly used as research tools but they have great potential as diagnostic devices and as a reliable means of predicting a patients' susceptibility to various diseases.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

DNA microarray

an orderly, low density arrangement of DNA samples, for example cDNA (see COPY DNA), immobilized as spots on a matrix. DNA microarrays can be fabricated by robotic spotting of single-stranded DNA PROBE molecules, on to the surface of a microscope slide, such that DNA of known identity is immobilized at precisely defined locations. A single slide may contain information for thousands of genes.

A typical DNA microarray/chip experiment involves matching known (probe) and unknown (target) nucleic acid samples on the basis of COMPLEMENTARY BASE PAIRING through HYBRIDIZATION, and automating the process of identifying the unknowns.

The target single-stranded nucleic acid sample, DNA or RNA, whose identity/ abundance is being determined, is labelled (see LABEL for example using a fluorescent dye, and incubated with the microarray/chip so that hybridization can occur between probe and target. Any unhybridized, free nucleic acid is washed away and HYBRID molecules detected by scanning and locating the positions of the fluorescent label. Abundance depends on the amount of fluorescence, whilst the position of fluorescence identifies the sample.

[Note: the definitions for the terms ‘probe’ and ‘target’ as used here differ from those used in classical hybridization. Here, the probe is immobilized and unlabelled, whilst the target is free and labelled.]

A problem with the use of microarrays is the potential for intra-strand BASE PAIRING in nucleic acid molecules, which could block probe-target interactions and hybrid formation. The use of PNA probes may circumvent this, since PNA:DNA hybrids can form under conditions that inhibit intra-strand base pairing in single-stranded DNA.

Microarrays/chips allow a large number of hybridization experiments to be carried out simultaneously in a single assay, so that thousands of GENES could be analysed in parallel. The technology can be used for a number of purposes including

  1. identification of genes;
  2. determination of the level of GENE/GENOME EXPRESSION in, for example, normal cells or tissues, diseased states, cell cycle analysis, and response to environmental stimuli;
  3. Detection of MUTATIONS and POLYMORPHISMS. For gene expression studies mRNA or cDNA is prepared and used to hybridize to specific probes. Hybrids identify the expressed genes.

Applications of the technology include drug discovery and development, human and agricultural diagnostics (see DIAGNOSIS), analysis of food and GMOs, SNP identification, and screening for TOXINS (see TOXICOGENOMICS).

DNA microarrays/chips are important tools in functional GENOMICS.

The terms ‘DNA microarray’ and ‘DNA chip’ are often used interchangeably although there is a technical difference. Other terminologies include biochip, gene chip, gene array

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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Most recently, he has used DNA microarrays to analyze the bacterial response to conditions encountered within the host during infection.
Publicly available software tools have been developed to help in the interpretation and analyses of DNA microarray data.
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The commercial global market for DNA microarrays is expected to grow at nearly 7% CAGR from about $600 million in 2003 to nearly $1 billion by 2010, according to a recent study by the London office of market consultant Frost & Sullivan.
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Some specific areas detailed in the book's 19 chapters are the Mexican-hat wavelet, image analysis and data mining for DNA microarray processing, rejection and interpolation based techniques for structured and impulsive noise filtering, and the link between bolstered classification error and dataset complexity for gene expression based cancer classification.
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