[Novel approaches; improved diagnosis and therapy with DNA microarrays. I. Technology and data analysis]

With DNA microarrays it will be possible to refine diagnostics and treatment with the use of genome wide information on a patient's sample. Microarrays are currently applied to unravel gene functions, pathogenetic mechanisms, metabolic routes and the effects of drugs on these, to refine diagnostic classifications and prognostic indexes, and to find new targets for therapy. With genotyping it will be possible to generate risk profiles for certain diseases and to assess the likelihood of a given drug-related side effect. Furthermore, it may accelerate research of mutations in genes for which the normal DNA sequences are already known. The basic principle of DNA microarrays is that thousands of different DNA sequences, each specific for a given gene, are immobilised on a solid surface (for example a microscope slide), arranged in a known order, and are hybridised with a solution of labelled DNA or RNA molecules. The DNA or RNA molecules under investigation bind to complementary base pairs on the slide, and permit us to measure the amount of labelled DNA or RNA hybridised to each gene sequence. Sophisticated software is used to analyse the large amount of data generated. The ultimate aim is to group genes with similar expression patterns across all samples, and then group samples accordingly. Conventional biological or biochemical techniques are required to validate the data obtained with microarrays, and to verify whether the observed associations among genes are biologically relevant.