What Is A DNA-chip?

A DNA microarray (also commonly known as gene or genome chip, DNA chip, or gene array) is a collection of microscopic DNA spots attached to a solid surface, such as glass, plastic or silicon chip forming an array for the purpose of expression profiling, monitoring expression levels for thousands of genes simultaneously, or for comparative genomic hybridization.

The affixed DNA segments are known as probes (although some sources will use different nomenclature such as reporters), thousands of which can be placed in known locations on a single DNA microarray. Microarray technology evolved from Southern blotting, whereby fragmented DNA is attached to a substrate and then probed with a known gene or fragment. Measuring gene expression using microarrays is relevant to many areas of biology and medicine, such as studying treatments, disease, and developmental stages. For example, microarrays can be used to identify disease genes by comparing gene expression in diseased and normal cells.

It probably refers to the technology where specific sequences of DNA or oligonucleotides are bound to a surface that is then used to detect particular DNA sequences in a sample prepared from cells of tissue.  The technology has evolved significantly since the sequencing of the Human Genome, and there are many variations of the technology.  The best source of information comes from the literature as well as the manufacturers of the technology.  The two best sources of information are:

Affymetrix (www.affymetrix.com) is the first company to mass produce DNA-chips, and Illumina (www.illumina.com) has come up with a new platform technology to supercede the capacity in terms of number of sequences and the analysis that can be performed.