Bibliographie

Consistent progress has been obtained in recent years in the diagnosis and understanding of genetic disease. High resolution chromosome analysis has narrowed the gap between cytogenetics and Mendelism by proving that some diseases considered to be due to monogenic inheritance result in fact from deletion of contiguous genes or breakage of a specific gene. Gene "imprinting" has been found to be the cause of some syndromes, such as the Prader-Willi, Angelman, and Beckwith-Wiedemann. Molecular cytogenetics has become a tool for analysing small rearrangements not easily seen using traditional chromosome analysis, for detecting mosaicisms, and narrowing the "critical" regions of chromosomal syndromes. "Positional cloning" techniques have improved our ability to map disease-genes. Linkage studies and direct analysis of cloned genes are now having a large impact on the analysis of genetic diseases segregating in families, and in testing for healthy heterozygotes and presymptomatic patients. Discovery of mutations in the mitochondrial genome has widened our understanding of disease inheritance. A few disorders have been shown to be due to tandem amplification of GC-rich intragenic triplets. Genetic counseling has taken advantage of these improvements which have a large impact on our knowledge of genetic heterogeneity and variability.