[Molecular genetics: a new approach of clinical neurosciences].

Genetically determined diseases with neurological expression are frequent. Recent progress in molecular biological techniques, particularly the availability of markers distributed throughout the whole human genome, has given birth to the concept of reverse genetics, with consists in localizing the gene responsible for a disease, then identifying it and its corresponding protein. This approach is illustrated by the studies that led to the localization of the gene responsible for Huntington's chorea on the short arm of chromosome 4 and the identification of dystrophic, the abnormal gene product in Duchenne's and Becker's muscular dystrophies. These discoveries have medical repercussions, leading to predictive tests or new therapies. However, predictive medicine raises ethical issues that are largely debated.