[Fifty years of medical genetics. A tribute to Maurice Lamy on the hundredth anniversary of his birth]. / Un demi-siècle de génétique Médicale. un hommage à Maurice Lamy, pour le centième anniversaire de sa naissance.

Before 1960, no disease gene had been mapped to human chromosome apart from the sex-linked characters which are carried by the X chromosome. The first assignments were inferred from the results of somatic cells hydridization and concerned enzymatic deficiencies and protein defects. They were followed by the data gained from the cytogenetics studies of microrearrangements, either deletions or translocations. The family and linkage studies began to be successfully undertaken following the discovery of polymorphic probes. The breakthrough came out with the availability of highly polymorphic microsatellites scanning quite evenly, the major part of the genome. Currently, more than 1,000 clinical disorders are mapped and compiled in the database GID/GENATLAS. They concern all chapters and extend to characters which are usually sporadic, such as malignant tumours and congenital malformations. The mapping endeavour already had great impact on our understanding of fundamental life processes and unveiled the extent of genetic heterogeneity of diseases. Its major consequences concern prenatal diagnosis. The applications tend to extend towards presymptomatic diagnosis, and screening of carriers, two procedures still controversial, which request due consideration of their inherent risks and side effects and cannot be undertaken without the informed consent of patients. Predictive testing for the detection of liabilities is still a subject of lively debate. Although the spectacular advances of mapping and its implications open great hopes for the prevention and even cure of disease, care has to be taken to their limits and risks and, in their approach, full consideration must be given the respect if human person.