The DNA Microarray:

        Approaching Personalized Medicine

What is a DNA-Microarray?    Fabrication    Gene Expression Profiling

The DNA-microarray evolved in the early 90s through the pioneering research of RB Ekins et al. of Boehringer Mannheim, Stephen Fodor et al. of Affymetrix, Inc. and Patrick O. Brown of Stanford University.  The two primary concepts which led to the development and use of the DNA-microarray.

• The amount of a particular substance in a mixture of substances can be determined through a probe/target interaction on a ligand assay. 
• DNA can be labeled for detection as it is when using the Southern blot.

The DNA-microarray uses either cDNA or other oligonucleotides as probes.  These probes are allowed to hybridize with their fluorescently labeled target DNA strands.  The fluoresce is then detected with either a scanning confocal microscope or a CCD device.  Data analysis is then used to determine the relative amounts, or expression, or the DNA targets.   Where traditional assays used macro spotting techniques resulting relatively large, 300 plus micron diameter spots.  The microarray uses advanced techniques to produce spots that are only ten of microns in diameter which can be placed in extremely high densities on a slide.  Similar to the Southern blot the targets for these spotted probes are fluorescently labeled DNA strands.  However, the use of a non-porous surface allows for greater miniaturization, quicker hybridization, a easier fluorescence detection.

A DNA-Microarray can test for tens of thousands of gene transcripts at the same time and therefore under the same conditions.  This high-throughput is ideal for three main purposes.

• Arrays to Identify Patterns - Testing globally for disease-specific patterns, a gene-expression or signature often of fewer than 50 genes can be characterized.  This is were majority of research is concerned.  However, the large labor and material requirements for this type of testing does not make it ideal to use for more routine purposes.
• Arrays to Measure Patterns - Rather than global testing, here only specifically selected and validated probes are used to test for a specific pattern.  As pricing and ease of use improve, these "focused arrays" may eventually become regularly used in diagnostics and drug discovery.
• Arrays for Parallel Processing - Beyond the focus of this site, microarrays can be used whenever a process will benefit from massively parallel processing.

In addition to DNA-microarrays, researchers have also developed protein microarrays, tissue microarrays, and even whole cell microarrays.

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Site creator: Fred Ayers