[DNA chips]

Abstract

DNA chips represent a miniaturization of the classical system of reverse dot-blot. They consist of a small size support made of plastic or glass or silicium on which probes are synthesized or immobilized. It is thus possible to fix a few thousand or even a hundred of thousands of probes per cm2. Practically the chips are hybridized with the nucleic acid to be studied that has been amplified beforehand by PCR and which is generally labelled by a fluorochrome, either during amplification or after hybridization. After washing the hybrids are detected by a system which most of the time consists of a laser and a confocal microscope interfaced with a computer, but many variations exist. It is thus possible to analyse at the same time a considerable number of sequences. The diagnostic applications are only at the prototype stage. Eventually the chips should allow the identification of any point mutation, or the search for bacteria, viruses or parasites in a very short period of time without preliminary cultures. They should also allow many sorts of typing ranging from infectious agents to HLA. They should become a particularly powerful tool in the search for new medicines and in the revealing of their toxicity. A considerable potential market is also the diagnosis of the predisposition to polygenic diseases or to a particular sensitivity to any chemical substance. In fact the chips are only just beginning to be used. One of the foreseeable developments should be the possibility to study nucleic acids without preliminary amplification and we can hope to eventually have at our disposal very cheap, autonomous integrated systems. The technology could eventually extend to fields other than molecular biology such as immunology or biochemistry.