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Encyclopedia > DNA microarray
Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail.
For terminology, see glossary below

A DNA microarray is a high-throughput technology used in molecular biology and in medicine. It consists of an arrayed series of thousands of microscopic spots of DNA oligonucleotides, called features, each containing picomoles of a specific DNA sequence. 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 fluorescence-based detection of fluorophore-labeled targets to determine relative abundance of nucleic acid sequences in the target. Image File history File links Download high resolution version (835x507, 133 KB) Summary Example of an approximately 37,500 probe spotted oligo microarray with enlarged inset to show detail Licensing I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high resolution version (835x507, 133 KB) Summary Example of an approximately 37,500 probe spotted oligo microarray with enlarged inset to show detail Licensing I, the creator of this work, hereby release it into the public domain. ... Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail. ... High-throughput may refer to: Throughput - a Computer science concept High-throughput_screening - a Bioinformatics concept Throughput_accounting - an Accounting concept Measuring_data_throughput - a Communications concept This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Molecular biology is the study of biology at a molecular level. ... For the chemical substances known as medicines, see medication. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Oligonucleotides are short sequences of nucleotides (RNA or DNA), typically with twenty or fewer bases. ... For other meanings of Pico see Pico (disambiguation) Pico (symbol p) is a prefix in the SI system of units denoting a factor of 10-12. ... Look up mole in Wiktionary, the free dictionary. ... For other uses, see Gene (disambiguation). ... Hybridization is the process, discovered by Alexander Rich, of combining complementary, single-stranded nucleic acids into a single molecule. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... A fluorophore-labeled human cell. ...


In standard microarrays, the probes are attached 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 commonly known as gene chip or colloquially Affy chip when an Affymetrix chip is used. Other microarray platforms, such as Illumina, use microscopic beads, instead of the large solid support. 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. Covalent redirects here. ... In chemistry, epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... Lysine is one of the 20 amino acids normally found in proteins. ... Polyacrylamide is an acrylate polymer formed from acrylamide subunits that is readily cross-linked. ... Affymetrix Logo Affymetrix NASDAQ: AFFX was founded by Stephen P.A. Fodor, Ph. ... Illumina (NASDAQ: ILMN) has developed a targeted set of instruments and chips for organizations conducting larger-scale research in genotyping and gene expression profiling. ...


DNA microarrays can be used to measure changes in expression levels or to detect single nucleotide polymorphisms (SNPs) (see Types of arrays 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). Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... DNA strand 1 differs from DNA strand 2 at a single base-pair location (a C/T polymorphism). ... Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail. ... Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail. ... Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail. ...

Contents

History

Microarray technology evolved from Southern blotting, where fragmented DNA is attached to a substrate and then probed with a known gene or fragment. The use of a collection of distinct DNAs in arrays for expression profiling was first described in 1987, and the arrayed DNAs were used to identify genes whose expression is modulated by interferon.[1] These early gene arrays were made by spotting cDNAs onto filter paper with a pin-spotting device. The use of miniaturized microarrays for gene expression profiling was first reported in 1995, [2] and a complete eukaryotic genome (Saccharomyces cerevisiae) on a microarray was published in 1997. [3] A Southern blot is a method in molecular biology of enhancing the result of an agarose gel electrophoresis by marking specific DNA sequences. ... For other uses, see Substrate. ... Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid flow and is used to separate fine solids from liquids. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Binomial name Meyen ex E.C. Hansen Saccharomyces cerevisiae is a species of budding yeast. ...


Uses and types

Two Affymetrix chips
Two Affymetrix chips

Arrays of DNA can be spatially arranged, as in the commonly known gene chip (also called genome chip, DNA chip or gene array), or can be specific DNA sequences labelled such that they can be independently identified in solution. The traditional solid-phase array is a collection of microscopic DNA spots attached to a solid surface, such as glass, plastic or silicon biochip. The affixed DNA segments are known as probes (although some sources use different terms such as reporters). Thousands of them can be placed in known locations on a single DNA microarray. Image File history File links Download high resolution version (665x603, 130 KB) Summary Two Affymetrix chips. ... Image File history File links Download high resolution version (665x603, 130 KB) Summary Two Affymetrix chips. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... This article is about the material. ... For other uses, see Plastic (disambiguation). ... Not to be confused with Silicone. ... The development of biochips is a major thrust of the rapidly growing biotechnology industry, which encompasses a very diverse range of research efforts including genomics, proteomics, computational biology, and pharmaceuticals, among other activities. ...


DNA microarrays can be used to detect DNA (as in comparative genomic hybridization), or detect of RNA (most commonly as cDNA after reverse transcription) that may or may not be translated into proteins. The process of measuring gene expression via cDNA is called expression analysis or expression profiling. Comparative genomic hybridization (CGH) is a molecular-cytogenetic method for the analysis of regional changes in the DNA content of tumor cells. ... In genetics, complementary DNA (cDNA) is single-stranded DNA synthesized from a mature mRNA template. ... Reverse transcriptase is an enzyme used by all retroviruses and retrotransposons that transcribes the genetic information from the virus or retrotransposon from RNA into DNA, which can integrate into the host genome. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... Expression Profiling Microarray technology is often used for expression profiling. ...


Since an array can contain tens of thousands of probes, a microarray experiment can accomplish that many genetic tests in parallel. Therefore arrays have dramatically accelerated many types of investigation. Applications include:


Gene expression profiling

Main article: expression profiling

In an mRNA or gene expression profiling experiment the expression levels of thousands of genes are simultaneously monitored to study the effects of certain treatments, diseases, and developmental stages on gene expression. For example, microarray-based gene expression profiling can be used to identify genes whose expression is changed in response to pathogens or other organisms by comparing gene expression in infected to that in uninfected cells or tissues. [4] Expression Profiling Microarray technology is often used for expression profiling. ... The interaction of mRNA in a eukaryote cell. ... Expression Profiling Microarray technology is often used for expression profiling. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... This article is about the medical term. ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ...


Comparative genomic hybridization

Assessing genome content in different cells or closely related organisms. [5] [6] Comparative genomic hybridization (CGH) is a molecular-cytogenetic method for the analysis of regional changes in the DNA content of tumor cells. ...


SNP detection

Main article: SNP array

Identifying single nucleotide polymorphism among alleles within or between populations.[7] It has been suggested that this article or section be merged into DNA microarray. ... DNA strand 1 differs from DNA strand 2 at a single base-pair location (a C/T polymorphism). ... An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. ...


Chromatin immunoprecipitation on Chip

Main article: ChIP-on-chip

DNA sequences bound to a particular protein can be isolated by imunoprecipitating that protein (ChIP), these fragments can be then hybridized to a microarray (such as a tiling array) allowing the determination of protein binding site occupancy throughout the genome. Example protein to imunoprecipitate are histone modifications (H3K27me3, H3K4me2, H3K9me3, etc), Polycomb-group protein (PRC2:Suz12, PRC1:YY1) and trithorax-group protein (Ash1) to study the epigenetic landscape or RNA Polymerase II to study the transcription lanscape. Workflow overview of a ChIP-on-chip experiment. ... Immunoprecipitation is the technique of precipitating an antigen out of solution using an antibody specific to that antigen. ... Chromatin immunoprecipitation (ChIP) assay, is an experimental method used in molecular biology. ... Chromatin immunoprecipitation (ChIP) assay, is an experimental method used in molecular biology. ... Epigenetics is a term in biology used today to refer to features such as chromatin and DNA modifications that are stable over rounds of cell division but do not involve changes in the underlying DNA sequence of the organism. ... RNA polymerase II (also called RNAP II and Pol II) transcribes DNA to synthesize precursors of mRNA and most snRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase. ... Look up Transcription in Wiktionary, the free dictionary. ...


Genotyping

Main article: SNP array

DNA microarrays can also be used to scan the entire sequence of a genome to identify genetic variation at certain locations. It has been suggested that this article or section be merged into DNA microarray. ...


SNP microarrays are a type of DNA microarray that are used to identify genetic variation in individuals and across populations. [7] Short oligonucleotide arrays can be used to identify single nucleotide polymorphisms (SNPs) responsible for genetic variation and the potential source of susceptibility to genetically caused diseases. Generally termed genotyping applications, DNA microarrays may be used in this fashion for forensic applications, genotyping, rapidly discovering or measuring genetic predisposition to disease, or identifying DNA-based drug candidates. A Single Nucleotide Polymorphism or SNP (pronounced snip) is a DNA sequence variation, occurring when a single nucleotide: adenine (A), thymine (T), cytosine (C) or guanine (G) - in the genome is altered. ... Genotyping refers to the process of determining the genotype of an individual with a biological assay. ...


These SNP microarrays are also being used to profile somatic mutations in cancer, specifically loss of heterozygosity events and amplifications and deletions of regions of DNA. Amplifications and deletions can also be detected using comparative genomic hybridization (CGH) in conjunction with microarrays, but may be limited in detecting novel Copy Number Polymorphisms, or CNPs, by probe coverage. The term somatic refers to the body, as distinct from some other entity, such as the mind. ... This article is about mutation in biology, for other meanings see: mutation (disambiguation). ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Loss of heterozygosity in a cell represents the loss of a single parents contribution to part of its genome. ... Comparative genomic hybridization (CGH) is a molecular-cytogenetic method for the analysis of regional changes in the DNA content of tumor cells. ...


Resequencing

Resequencing arrays have been developed to sequence portions of the genome in individuals. These arrays may be used to evaluate germline mutations in individuals, or somatic mutations in cancers.[citation needed] In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Germline is a word used in biology and genetics. ...


Tiling

Genome tiling arrays include overlapping oligonucleotides designed to cover an entire genomic region of interest. Many companies have successfully designed tiling arrays that cover whole human chromosomes.


Fabrication

Microarrays can be manufactured in different ways, depending on the number of probes under examination, costs, customization requirements, and the type of scientific question being asked. Arrays may have as few as 10 probes to up to 390,000 micron-scale probes from commercial vendors.


Spotted vs. oligonucleotide arrays

A DNA microarray being created

A DNA microarray being printed by a robot at the University of Delaware. • File format: Ogg• File size: 5.05 MB• Duration: 1m11s Wikipedia does not have an article with this exact name. ... For other uses, see robot (disambiguation). ... The University of Delaware (UD) is the largest university in the U.S. state of Delaware. ... Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ...

Wikipedia:Media help


Microarrays can be fabricated using a variety of technologies, including printing with fine-pointed pins onto glass slides, photolithography using pre-made masks, photolithography using dynamic micromirror devices, ink-jet printing, [8] or electrochemistry on microelectrode arrays. Photolithography is a process used in semiconductor device fabrication to transfer a pattern from a photomask (also called reticle) to the surface of a substrate. ... English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ...


In spotted microarrays, the probes are oligonucleotides, cDNA or small fragments of PCR products that correspond to mRNAs. The probes are synthesized prior to deposition on the array surface and are then "spotted" onto glass. A common approach utilizes an array of fine pins or needles controlled by a robotic arm that is dipped into wells containing DNA probes and then depositing each probe at designated locations on the array surface. The resulting "grid" of probes represents the nucleic acid profiles of the prepared probes and is ready to receive complementary cDNA or cRNA "targets" derived from experimental or clinical samples. This technique is used by research scientists around the world to produce "in-house" printed microarrays from their own labs. These arrays may be easily customized for each experiment, because researchers can choose the probes and printing locations on the arrays, synthesize the probes in their own lab (or collaborating facility), and spot the arrays. They can then generate their own labeled samples for hybridization, hybridize the samples to the array, and finally scan the arrays with their own equipment. This provides a relatively low-cost microarray that is customized for each study, and avoids the costs of purchasing often more expensive commercial arrays that may represent vast numbers of genes that are not of interest to the investigator. Publications exist which indicate in-house spotted microarrays may not provide the same level of sensitivity compared to commercial oligonucleotide arrays, [9] possibly owing to the small batch sizes and reduced printing efficiencies when compared to industrial manufactures of oligo arrays. Applied Microarrays offers a commercial array platform called the "CodeLink" system where 30-mer oligonucleotide probes (sequences of 30 nucleotides in length) are piezoelectrically deposited on an acrylamide matrix without any contact being made between the depositing equipment and the array surface itself. These arrays are comparable in quality to most manufactured arrays and generally superior to in-house printed arrays.[citation needed] Oligonucleotide synthesis is the non-biological, chemical synthesis of defined short sequences of nucleic acids. ... In genetics, complementary DNA (cDNA) is single-stranded DNA synthesized from a mature mRNA template. ... Wikipedia does not yet have an article with this exact name. ... The interaction of mRNA in a eukaryote cell. ... Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ...


In oligonucleotide microarrays, the probes are short sequences designed to match parts of the sequence of known or predicted open reading frames. Although oligonucleotide probes are often used in "spotted" microarrays, the term "oligonucleotide array" most often refers to a specific technique of manufacturing. Oligonucleotide arrays are produced by printing short oligonucleotide sequences designed to represent a single gene or family of gene splice-variants by synthesizing this sequence directly onto the array surface instead of depositing intact sequences. Sequences may be longer (60-mer probes such as the Agilent design) or shorter (25-mer probes produced by Affymetrix) depending on the desired purpose; longer probes are more specific to individual target genes, shorter probes may be spotted in higher density across the array and are cheaper to manufacture. One technique used to produce oligonucleotide arrays include photolithographic synthesis (Agilent and Affymetrix) on a silica substrate where light and light-sensitive masking agents are used to "build" a sequence one nucleotide at a time across the entire array. [10] Each applicable probe is selectively "unmasked" prior to bathing the array in a solution of a single nucleotide, then a masking reaction takes place and the next set of probes are unmasked in preparation for a different nucleotide exposure. After many repetitions, the sequences of every probe become fully constructed. More recently, Maskless Array Synthesis from NimbleGen Systems has combined flexibility with large numbers of probes. [11] An open reading frame or ORF is any sequence of DNA or RNA that can be translated into a protein. ... ... Affymetrix Logo Affymetrix NASDAQ: AFFX was founded by Stephen P.A. Fodor, Ph. ... This article discusses the modern manufacture of semiconductors. ...


Two-channel vs. one-channel detection

Diagram of typical dual-colour microarray experiment.
Diagram of typical dual-colour microarray experiment.

Two-color microarrays or two-channel microarrays are typically hybridized with cDNA prepared from two samples to be compared (e.g. diseased tissue versus healthy tissue) and that are labeled with two different fluorophores. [12] Fluorescent dyes commonly used for cDNA labelling include Cy3, which has a fluorescence emission wavelength of 570 nm (corresponding to the green part of the light spectrum), and Cy5 with a fluorescence emission wavelength of 670 nm (corresponding to the red part of the light spectrum). The two Cy-labelled cDNA samples are mixed and hybridized to a single microarray that is then scanned in a microarray scanner to visualize fluorescence of the two fluorophores after excitation with a laser beam of a defined wavelength. Relative intensities of each fluorophore may then be used in ratio-based analysis to identify up-regulated and down-regulated genes. [13] Hybridization is the process of combining complementary, single-stranded nucleic acids into a single molecule. ... A fluorophore-labeled human cell. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Cyanine Cyanine is a polymer hydroxide formula achieved in 1986 by the Universal Chemical Society. ... Cyanine Cyanine is a polymer hydroxide formula achieved in 1986 by the Universal Chemical Society. ... Excitation is the amount of energy (energy in a general sense, not energy as defined in physics) that Curtis has. ... For other uses, see Laser (disambiguation). ...


Oligonucleotide microarrays often contain control probes designed to hybridize with RNA spike-ins. The degree of hybridization between the spike-ins and the control probes is used to normalize the hybridization measurements for the target probes. Although absolute levels of gene expression may be determined in the two-color array, the relative differences in expression among different spots within a sample and between samples is the preferred method of data analysis for the two-color system. Examples of providers for such microarrays includes Agilent with their Dual-Mode platform, Eppendorf with their DualChip platform for fluorescence labeling, and TeleChem International with Arrayit. There are very few or no other articles that link to this one. ... In one usage in statistics, normalization is the process of removing statistical error in repeated measured data. ... Data analysis is the act of transforming data with the aim of extracting useful information and facilitating conclusions. ... ... An Eppendorf thermomixer. ...


In single-channel microarrays or one-color microarrays, the arrays are designed to give estimations of the absolute levels of gene expression. Therefore the comparison of two conditions requires two separate single-dye hybridizations. As only a single dye is used, the data collected represent absolute values of gene expression. These may be compared to other genes within a sample or to reference "normalizing" probes used to calibrate data across the entire array and across multiple arrays. Three popular single-channel systems are the Affymetrix "Gene Chip", the Applied Microarrays "CodeLink" arrays, and the Eppendorf "DualChip & Silverquant". One strength of the single-dye system lies in the fact that an aberrant sample cannot affect the raw data derived from other samples, because each array chip is exposed to only one sample (as opposed to a two-color system in which a single low-quality sample may drastically impinge on overall data precision even if the other sample was of high quality). Another benefit is that data are more easily compared to arrays from different experiments; the absolute values of gene expression may be compared between studies conducted months or years apart. A drawback to the one-color system is that, when compared to the two-color system, twice as many microarrays are needed to compare samples within an experiment.


Microarrays and bioinformatics

Gene expression values from microarray experiments can be represented as heat maps to visualize the result of data analysis.
Gene expression values from microarray experiments can be represented as heat maps to visualize the result of data analysis.

Image File history File links Download high-resolution version (1400x1400, 92 KB) This image was generated in an academic institution using public data and public software. ... Image File history File links Download high-resolution version (1400x1400, 92 KB) This image was generated in an academic institution using public data and public software. ... Heat map generated from DNA microarray data reflecting gene expression values in several conditions A heat map is a graphical representation of data where the values taken by a variable in a two-dimensional map are represented as colours. ...

Experimental Design

Due to the biological complexity of gene expression, the considerations of experimental design that are discussed in the expression profiling article are of critical importance if statistically and biologically valid conclusions are to be drawn from the data. Expression Profiling Microarray technology is often used for expression profiling. ...


There are three main elements to consider when designing a microarray experiment. First, replication of the biological samples is essential for drawing conclusions from the experiment. Second, technical replicates (two RNA samples obtained from each experimental unit) help to ensure precision and allow for testing differences within treatment groups. The technical replicates may be two independent RNA extractions or two aliquots of the same extraction. Third, spots of each cDNA clone or oligonucleotide are present as replicates (at least duplicates) on the microarray slide, to provide a measure of technical precision in each hybridization. It is critical that information about the sample preparation and handling is discussed, in order to help identify the independent units in the experiment and to avoid inflated estimates of statistical significance.[14] In mathematics, an aliquot part (or simply aliquot) of an integer is any of its integer divisors. ... In statistics, a result is called statistically significant if it is unlikely to have occurred by chance. ...


Standardization

Microarray data is difficult to exchange due to the lack of standardization in arrays. This presents an interoperability problem in bioinformatics. Various grass-roots open-source projects are trying to ease the exchange and analysis of data produced with non-proprietary chips: Interoperability is a property referring to the ability of diverse systems and organizations to work together (inter-operate). ... Map of the human X chromosome (from the NCBI website). ... Grassroots democracy is the political processes which are driven by groups of ordinary citizens, as opposed to larger organisations or wealthy individuals with concentrated vested interests in particular policies. ... Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ...

  • For example, the "Minimum Information About a Microarray Experiment" (MIAME) checklist helps define the level of detail that should exist and is being adopted by many journals as a requirement for the submission of papers incorporating microarray results. But MIAME does not describe the the format for the information, so while many formats can support the MIAME requirements, as of 2007 no format permits verification of complete semantic compliance.
  • The "MicroArray Quality Control (MAQC) Project" is being conducted by the US Food and Drug Administration (FDA) to develop standards and quality control metrics which will eventually allow the use of MicroArray data in drug discovery, clinical practice and regulatory decision-making. [15]
  • The MicroArray and Gene Expression Data (MGED) group is working on the standardization of the representation of gene expression data and relevant annotations.

Minimum Information About a Microarray Experiment (MIAME) is a standard aimed at facilitating the dissemination of data from microarray experiments. ... Nature, Science and PNAS In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. ... FDA redirects here. ...

Statistical analysis

The analysis of DNA microarrays poses a large number of statistical problems, including the normalization of the data. There are dozens of proposed normalization methods in the published literature; as in many other cases where authorities disagree, a sound conservative approach is to try a number of popular normalization methods and compare the conclusions reached: how sensitive are the main conclusions to the method chosen? This article is about the field of statistics. ... In one usage in statistics, normalization is the process of removing statistical error in repeated measured data. ...


Also, experimenters must account for multiple comparisons: even if the statistical P-value assigned to a gene indicates that it is extremely unlikely that differential expression of this gene was due to random rather than treatment effects, the very high number of genes on an array makes it likely that differential expression of some genes represent false positives or false negatives. Statistical methods tailored to microarray analyses have recently become available that assess statistical power based on the variation present in the data and the number of experimental replicates, and can help minimize type I and type II errors in the analyses.[16] In statistics, the multiple comparisons problem tests null hypotheses stating that the averages of several disjoint populations are equal to each other (homogeneous). ... In statistical hypothesis testing, the p-value of a random variable T used as a test statistic is the probability that T will assume a value at least as extreme as the observed value tobserved, given that a null hypothesis being considered is true. ... Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors. ... Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors. ...


A basic difference between microarray data analysis and much traditional biomedical research is the dimensionality of the data. A large clinical study might collect 100 data items per patient for thousands of patients. A medium-size microarray study will obtain many thousands of numbers per sample for perhaps a hundred samples. Many analysis techniques treat each sample as a single point in a space with thousands of dimensions, then attempt by various techniques to reduce the dimensionality of the data to something humans can visualize. [17]


Relation between probe and gene

The relation between a probe and the mRNA that it is expected to detect is problematic. On the one hand, some mRNAs may cross-hybridize probes in the array that are supposed to detect another mRNA. On the other hand, probes that are designed to detect the mRNA of a particular gene may be relying on genomic EST information that is incorrectly associated with that gene. An expressed sequence tag or EST is a short sub-sequence of a transcribed spliced nucleotide sequence (either protein-coding or not). ...


Public databases of microarray data

Database Microarray experiment sets Sample profiles As of date
Gene Expression Omnibus - NCBI 8094 205148 March 11, 2008
Stanford Microarray database 12742  ? April 1, 2007
ArrayExpress at EBI 4194 110731 Mai, 2008
UPenn RAD database ~100 ~2500 Sept. 1, 2007
UNC Microarray database ~31 2093 April 1, 2007
MUSC database ~45 555 April 1, 2007
caArray at NCI 41 1741 November 15, 2006
UPSC-BASE ~100  ? November 15, 2007
Gemma 612 24513 March 3, 2008

The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The term microarray database is usually used to describe a database containing microarray gene expression data. ...

Online microarray data-analysis programs and tools

Several Open Directory Project categories list online microarray data analysis programs and tools: The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ...

The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... Genevestigator is a web-based application developed for biologists to rapidly find out in which tissues, at which stages of development, and to what stimuli, drug treatments, diseases, or genetic modifications genes of given organisms are activated. ... For the database, see IBM System R The R programming language, sometimes described as GNU S, is a programming language and software environment for statistical computing and graphics. ...

See also

Glass microfluidic devices from Syrris and Dolomite Microfluidics deals with the behavior, precise control and manipulation of microliter and nanoliter volumes of fluids. ... Cyanine Cyanine is a polymer hydroxide formula achieved in 1986 by the Universal Chemical Society. ... Serial analysis of gene expression (SAGE) is a technique used by molecular biologists to produce a snapshot of the messenger RNA population in a sample of interest. ...

References

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  2. ^ Schena M, Shalon D, Davis RW, Brown PO (1995). "Quantitative monitoring of gene expression patterns with a complementary DNA microarray". Science 270: 467-470. doi:10.1126/science.270.5235.467. PMID 7569999. 
  3. ^ Lashkari DA, DeRisi JL, McCusker JH, Namath AF, Gentile C, Hwang SY, Brown PO, Davis RW (1997). "Yeast microarrays for genome wide parallel genetic and gene expression analysis". Proc Natl Acad Sci USA 94: 13057-13062. doi:10.1073/pnas.94.24.13057. PMID 9371799. 
  4. ^ Adomas A, Heller G, Olson A, Osborne J, Karlsson M, Nahalkova J, Van Zyl L, Sederoff R, Stenlid J, Finlay R, Asiegbu FO (2008). "Comparative analysis of transcript abundance in Pinus sylvestris after challenge with a saprotrophic, pathogenic or mutualistic fungus". Tree Physiol. 28: 885-897. PMID 18381269. 
  5. ^ Pollack JR, Perou CM, Alizadeh AA, Eisen MB, Pergamenschikov A, Williams CF, Jeffrey SS, Botstein D, Brown PO (1999). "Genome-wide analysis of DNA copy-number changes using cDNA microarrays". Nat Genet 23: 41-46. doi:10.1038/14385. PMID 10471496. 
  6. ^ Moran G, Stokes C, Thewes S, Hube B, Coleman DC, Sullivan D (2004). "Comparative genomics using Candida albicans DNA microarrays reveals absence and divergence of virulence-associated genes in Candida dubliniensis". Microbiology 150: 3363-3382. doi:10.1099/mic.0.27221-0. PMID 15470115. 
  7. ^ a b Hacia JG, Fan JB, Ryder O, Jin L, Edgemon K, Ghandour G, Mayer RA, Sun B, Hsie L, Robbins CM, Brody LC, Wang D, Lander ES, Lipshutz R, Fodor SP, Collins FS (1999). "Determination of ancestral alleles for human single-nucleotide polymorphisms using high-density oligonucleotide arrays". Nat Genet 22: 164-167. doi:10.1038/9674. PMID 10369258. 
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18. Gomase VS, Tagore S, Kale KV. Microarray: an approach for current drug targets.Curr Drug Metab. 2008 Mar;9(3):221-31. [PMID: 18336225] A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

Glossary

  • Array (or slide): a collection of DNA samples representing different sequences spotted in two-dimensional grids, arranged in columns and rows.
  • Block or subarray: a group of spots, typically made in one print round; several subarrays/blocks form an array.
  • Case/control: an experimental condition chosen as control (such as healthy tissue or state) to which an altered condition (such as diseased tissue or state) is compared.
  • Candidate genes: genes which showed a significant change between the samples and so may be either genes regulated with a function relevant to the difference between the two samples, or be genes regulated due to bad genetic wiring, or be false positives.
  • Channel: the fluorescence output recorded in the scanner (see below) for an individual fluorophore and can even be ultraviolet.
  • Down-regulated: genes that show lower expression (lower mRNA levels) in one sample versus another sample (usually the control) under comparison.
  • Dye flip/swap: reciprocal labelling of DNA targets with the two dyes to account for dye bias in experiments.
  • Filter: a glass filter in front of a photomultiplier tube that allows transmission only of light of specific frequency.
  • Fluorophore: a molecule that has fluorescent properties; commonly used fluorophores include cyanine (Cy) dyes.
  • Hybridization: a solution containing single-stranded target DNA or RNA is added to the array surface to hybridize the DNA target to complementary probe sequences.
  • Library: a multi-well plate in which each well contains DNA probes, which are used for spotting on the array slide.
  • Oligonucleotide: a short (10-100 bases) DNA sequence; a "60-mer oligo" refers to the length of the oligonucleotide (60 bases in length).
  • Probe or reporter: single-stranded DNA that is covalently attached to the array surface.
  • Replication (statistics): a technique to estimate technical and biological variation in experiments for statistical analysis of the microarray data. Replicates may be:
    • technical replicates, such as dye swaps or repeated array hybridizations, or
    • biological replicates, using biological samples from separate experiments that test the effects of the same treatments.
  • Scanner: an instrument used to detect and quantify the intensity of fluorescence of spots on a microarray slide, by selectively exciting fluorophores with a laser and measuring the fluorescence with a filtered photomultiplier system.
  • Spot or feature: a small area on an array slide that contains picomoles of specific DNA samples; spots are spatially arranged on a two-dimensional array; features in electronic grids are aligned with spots for extraction of spot-intensity data.
  • Up-regulated: genes that are more highly expressed (higher mRNA levels) in one sample versus another (usually the control) under comparison.
  • For other terms see:
Glossary of gene expression terms
Protocol (natural sciences)

This article is actively undergoing a major edit. ... Gene regulation is the general term for cellular control of protein synthesis at the DNA-RNA transcription step. ... Coloured and Neutral Density filters An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, that is, range of colours of light), while blocking the remainder. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... For other uses, see Frequency (disambiguation). ... A fluorophore-labeled human cell. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Cyanine Cyanine is a polymer hydroxide formula achieved in 1986 by the Universal Chemical Society. ... On the left: nucleotides that forms the DNA and their complementary. ... Oligonucleotides are short sequences of nucleotides (RNA or DNA), typically with twenty or fewer bases. ... Covalent redirects here. ... In statistics, replication is the repetition of the creation of a phenomenon so that the variability associated with the phenomenon can be estimated. ... Multivariate analysis (MVA) is based on the statistical principle of multivariate statistics, which involves observation and analysis of more than one statistical variable at a time. ... For other uses, see Laser (disambiguation). ... See also: gene expression, List of Glossaries, List of Natural Sciences Glossaries A constitutive gene or constitutive expression describes a gene that is transcribed continually compared to a facultative gene which is only transcribed when needed. ... In the natural sciences, the terms protocol and method (as distinct from scientific method) are often used interchangeably. ...

External links

The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The Open Directory Project (ODP), also known as dmoz (from , its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors. ... The self-organizing map (SOM) is a subtype of artificial neural networks. ... Molecular biology is the study of biology at a molecular level. ... Information flow in biological systems The central dogma of molecular biology was first enunciated by Francis Crick in 1958[1] and re-stated in a Nature paper published in 1970:[2] POSTLEWAITE IS A TOOL The central dogma of molecular biology deals with the detailed residue-by-residue transfer of... DNA replication. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... For other uses, see RNA (disambiguation). ... Translation is the second stage of protein biosynthesis (part of the overall process of gene expression). ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Gene modulation redirects here. ... Epigenetics is a term in biology used today to refer to features such as chromatin and DNA modifications that are stable over rounds of cell division but do not involve changes in the underlying DNA sequence of the organism. ... Gene regulation is the general term for cellular control of protein synthesis at the DNA-RNA transcription step. ... Mitosis divides genetic information during cell division. ... It has been suggested that this article or section be merged into signal transduction. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Posttranslational modification means the chemical modification of a protein after its translation. ... A dry lab is a laboratory where computational or applied mathematical analyses are done on a computer generated model to simulate a phenomenon in the physical realm whether it be a molecule changing quantum states, the event horizon of a black hole or anything that otherwise might be too cumbersome... Wet Laboratories are defined as laboratories where chemicals, drugs, or other material or biological matter are tested and analyzed requiring water, direct ventilation, and specialized piped utilities. ... Views of a Foetus in the Womb, Leonardo da Vinci, ca. ... The history of molecular biology begins in the 1930s with the convergence of various, previously distinct biological disciplines: biochemistry, genetics, microbiology, and virology. ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ... The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc. ... A TATA box (also called Goldberg-Hogness box)[1] is a DNA sequence (Cis-regulatory element) found in the promoter region of most genes (it is considered to be the core promoter sequence) in eukaryotes [2]. It is the binding site of either transcription factors or histones (binding of a... An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ... The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. ... Trp operon is an anabolic operon which promotes the production of tryptophan in the absence of tryptophan in the environment. ... In genetics, a terminator marks the end of a gene on the DNA for transcription. ... In genetics, an enhancer is a short region of DNA that can be bound with proteins (namely, the trans-acting factors, much like a set of transcription factors) to enhance transcription levels of genes (hence the name) in a gene-cluster. ... A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing the rate of transcription. ... Lac Repressor molecule more details. ... The trp (tryptophan) repressor is a 25 kD protein which regulates transcription of the tryptophan biosynthetic pathway in bacteria. ... In genetics a silencer is a DNA sequence capable of binding transcription regulation factors termed repressors. ... Histone methylation is the modification of the primary protein sequence of a histone protein by the addition of an methyl group. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ... A model organism is one that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. ... C57BL/6, often referred to as C57 black 6 or just black 6 is a common inbred strain of lab mouse. ... Protein methods are the techniques used to study proteins. ... The tone or style of this article or section may not be appropriate for Wikipedia. ... Mass spectrometry (previously called mass spectroscopy (deprecated) or informally, mass-spec and MS) is an analytical technique that measures the mass-to-charge ratio of ions. ... This article is about the technology. ... Cell biology (also called cellular biology or formerly cytology, from the Greek kytos, container) is an academic discipline that studies cells. ... Wöhler observes the synthesis of urea. ... Computational biology is an interdisciplinary field that applies the techniques of computer science and applied mathematics to problems inspired by biology. ... See also: gene expression, List of Glossaries, List of Natural Sciences Glossaries A constitutive gene or constitutive expression describes a gene that is transcribed continually compared to a facultative gene which is only transcribed when needed. ... Academic organizations typically have a rather rigid set of ranks. ... This article is about the material. ... This article is about the material. ... This article is about the material. ... The glass transition temperature is the temperature below which the physical properties of amorphous materials vary in a manner similar to those of a solid phase (glassy state), and above which amorphous materials behave like liquids (rubbery state). ... In thermodynamics, the Kauzmann Paradox is the apparent result that it is possible to obtain a supercooled liquid with an entropy lower than that of its corresponding crystal. ... AgInSbTe, or Silver-Indium-Antimony-Tellurium, is a phase change material from the group of chalcogenide glasses, used in rewritable optical discs and phase-change memory applications. ... BioGlass® is a commercially available type of bioactive glass It is also known as 45S5 glass. ... Borophosphosilicate glass, commonly known as BPSG, is a type of silicate glass that includes impurities of both boron and phosphorus. ... It has been suggested that Kimax be merged into this article or section. ... Composite body, painted, and glazed bottle. ... A Chalcogenide glass is a glass containing a chalcogenide element (sulphur, selenium or tellurium) as a substantial constituent. ... Cobalt Glass Bromo-Seltzer bottle Cobalt glass is a deep blue colored glass prepared by adding cobalt compounds to the molten glass. ... Cranberry glass (or Gold Ruby glass as it is known in Europe) is a red glass made by adding gold chloride to the molten glass. ... Crown glass is a type of optical glass used in lenses. ... Flint glass is an optical glass that has relatively high refractive index and low Abbe number. ... Fluorosilicate glass (FSG) is a dielectric used in between copper metal layers during silicon integrated circuit fabrication process. ... A sphere manufactured by NASA out of fused quartz for use in a gyroscope in the Gravity Probe B experiment. ... GeSbTe, or Germanium-Antimony-Tellurium, is a phase change material from the group of chalcogenide glasses, used in rewritable optical discs and phase-change memory applications. ... Cranberry glass (or Gold Ruby glass as it is known in Europe) is a red glass made by adding gold chloride to the molten glass. ... Lead glass is potassium silicate glass which has been impregnated with lead oxide (from 12% to 28% by weight) in its fabrication. ... Milk glass is a white, opaque variety of glass. ... Phosphosilicate glass, commonly referred to by the acronym PSG, is a silicate glass commonly used in semiconductor device fabrication for intermetal layers, i. ... Photochromic lenses are lenses that darken on exposure to UV radiation. ... Silicate glasses have been commonly used in the field of semiconductor device fabrication as an insulator between active layers of the semiconductor device. ... Soda-lime glass is the kind of glass which is most widely used for various purposes. ... Sodium hexametaphosphate (SHMP) (E452(i)) is a hexamer of composition (NaPO3)6. ... Soluble glass is a popular name for sodium silicate or potassium silicate. ... Missing image A selection of uranium glasses Uranium farce, also known as vaseline farce, is a pale yellow or yellow-green glass made by the inclusion of uranium. ... In a discussion of art technology, enamel (or vitreous enamel, or porcelain enamel in American English) is the colorful result of fusion of powdered glass to a substrate through the process of firing, usually between 750 and 850 degrees Celsius. ... ZBLAN is a type of glass that is made of a mixture of Zirconium, Barium, Lanthium, Aluminum, and Sodium Flourides. ... Glass-ceramic is a mixture of glass and ceramic materials (mainly lithium-, silicon-, or aluminium-oxides) yielding a material that is impervious to even extreme temperature shocks. ... Bioactive glasses are a group of surface reactive glass-ceramics and include the original bioactive glass, Bioglass®. The biocompatibility of these glasses has led them to be investigated extensively for use as implant materials in the human body to repair and replace diseased or damaged bone. ... Corningware is a brand of tempered glass and ceramic dishes made by Corning Glass Works. ... There are very few or no other articles that link to this one. ... Macor® is a machineable glass-ceramic developed and sold by Corning Inc. ... Annealing, in glassblowing and lampworking, is the process of heating, and then slowly cooling glass to increase softness (ductility) and durability. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ... Glass properties can be calculated through statistical analysis of glass databases such as SciGlass and Interglad. ... Ion implantation is a materials engineering process by which ions of a material can be implanted into another solid, thereby changing the physical properties of the solid. ... The Liquidus Temperature, TL or Tliq, is mostly used for glasses and alloys. ... Sol gel is a colloidal suspension of silicon dioxide that is gelled to form a solid. ... For other uses, see Viscosity (disambiguation). ... For the book by Sir Isaac Newton, see Opticks. ... Dispersion of a light beam in a prism. ... Gradient index optics is the branch of optics covering optical effects produced by a gradual variation of the refractive index of a material. ... An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... Optical lens design is the science/art of calculating the various lens construction parameters (variables) that will meet or at least approach desired performance requirements while staying within required constraint values. ... Photochromic lenses are lenses that darken on exposure to UV radiation. ... For the property of metals, see refraction (metallurgy). ... Anti-reflective coatings are a type of optical coating applied to lenses and other devices to reduce reflection from optical surfaces. ... For the hazard, see corrosive. ... Insulated Glazing Unit or Insulating Glass Unit (commonly referred to as IGU) is described as two or more lites of glass spaced apart and hermetically sealed to form a single glazed unit with an air space between each lite. ... Sol gel is a colloidal suspension of silicon dioxide that is gelled to form a solid. ... A vandalized telephone booth with toughened glass Toughened glass or tempered glass is a type of glass that has increased strength and will usually shatter into small fragments when broken. ... diffusion (disambiguation). ... There are very few or no other articles that link to this one. ... Since the beginning of scientific glass research in the 19th century thousands of glass property-composition datasets were published in the scientific literature, in patents, and other sources. ... Glass electrode is a potentiometric sensor made from glass of f specific composition. ... Glass Ionomer Cements (GIC) are a class of materials commonly used in dentistry as filling materials and luting cements. ... Glass microspheres are spheres of glass technically manufactured with a diameter in the micrometer range (from 1 to 1000 (microns))[1], although the term is also used for a wider range of 100 nanometres to 5 millimetres. ... This article is about the material. ... It has been suggested that Fiber-reinforced plastic be merged into this article or section. ... Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. ... Panoramic (wrap-around) windshield on a 1959 Edsel Corsair. ...

  Results from FactBites:
 
Microarrays Factsheet (3611 words)
Microarrays are therefore useful when one wants to survey a large number of genes quickly or when the sample to be studied is small.
Microarrays may be used to assay gene expression within a single sample or to compare gene expression in two different cell types or tissue samples, such as in healthy and diseased tissue.
DNA Microarrays are small, solid supports onto which the sequences from thousands of different genes are immobilized, or attached, at fixed locations.
ENS microarray platform: DNA microarray principle (585 words)
DNA microarrays allow for rapid measurement and visualisation of differential expression between genes at the whole genome scale.
DNA fragments amplified by PCR technique are spotted on a microscopic glass slide coated with polylysine prior to spotting process.
Prior to hybridisation, DNA is denatured to obtained a single strand DNA on the microarray, this will allow the probe to bind to the complementary strand from the target.
  More results at FactBites »

 
 

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