The knowledge of the sequence of the entire human genome in 2001 brought new possibilities for molecular biology in clinical medicine. More and more genes, whose mutated functionless forms cause various diseases, are found every day. The aim of molecular biology for diagnostics purpose is to detect correctly and accurately the mutations in genes of patients suffering with high risk disease; to confirm or to refute the diagnosis of patients defined by doctors on the clinical or biochemical level; to reveal the disease in individuals who do not have any symptoms yet because they are at an early stage; to obtain knowledge about occurrence of mutant alleles in parents and siblings of patients and to make prenatal diagnosis of pregnant women with suspicion of duplicitas. The development of cancer and the effectiveness of its treatment can be detected on DNA or RNA level too. Present molecular genetics methods for the detection of mutations in genes are time and material consuming. That is why scientists focus on the new useful technologies based on DNA microarrays in the last years. The DNA microarrays allow to analyse whole spectrum of mutations and polymorphisms in various genes that cause hereditary diseases all at once. Thus, the DNA microarrays represent the possibility to speed up the analyses and lower its economical expensiveness.

        Key words: DNA chip, microarray, inherited diseases, molecular diagnostics.