DNA chips: a new tool for genetic analysis and diagnostics.

DNA chips are miniaturized microsystems based on the ability of DNA to spontaneously find and bind its complementary sequence in a highly specific and reversible manner, known as hybridization. Labeled DNA molecules in a sample are analyzed by DNA probes tethered at distinct sites on a solid support. The composition of the DNA sample is then deduced by analyzing the signal generated by labels present at each probe site. Applications are widespread: fundamental research, cancer or microbiology diagnostics, genotyping, gene expression, pharmacogenomics, and environmental control. Medical application consists, for example, in the identification and detection of mutations in genes responsible for cancers, or DNA chip analysis of individual polymorphisms which may provide a guide towards the most efficient treatment. In the environmental and agro-industrial fields, DNA chips show great promise in rapidly testing microorganism content, contamination or pathogenicity. DNA chip dimensions offer hybridization sites in the 50-200 micron range, producing arrays ranging from 100 to 1,000,000 different probes per cm2.