[Novel approaches; improved diagnostics and therapeutics with DNA microarrays. II. Applications]

The most important (future) applications of DNA microarrays in medicine are based on three different molecular analyses: gene expression analysis, genotyping with a specific type of microarray (single nucleotide polymorphism chip (SNP chip)), and DNA sequencing to search for a well-known mutation in a certain gene. With gene expression analysis one can obtain a 'molecular signature' of a tissue by allowing tissue RNA to react with a DNA microarray. This information may help to refine disease classifications, to guide the choice of therapy and to find new therapeutic targets. Genotyping utilizes genomic DNA that, after digestion, reacts with a SNP chip to obtain an individual SNP pattern. An SNP is a change of a single base pair within a gene sequence that can sometimes influence the function of the gene product. SNPs are considered to be variations in the genome and should be distinguished from mutations. These variations can for instance provide information about the probability of a certain disease, or the effectiveness or side effect of a certain drug. Sequencing well characterized genes to search for mutations is used to screen for genetic abnormalities. This process can be accelerated with the aid of oligonucleotide arrays. With this tool an individual's risk of developing certain forms of cancer or monogenetic diseases can be estimated.