[New developments in cytogenetics].

Novel methods allowing to analyze the human genome make it possible to assess old questions such as the molecular basis of structural chromosome anomalies and the diathesis to aneuploidy. The architecture of the human genome as unravelled by the human genome sequencing project allows to explain the recurrence of microdeletions and microduplications caused by a non allelic homologous recombination involving segmental duplications created during the evolution of primates. This structural feature of the human genome is associated with a novel class of genetic diseases called genomic disorders as opposed to genetic diseases due to gene mutations. The study of the parental and cellular origin of aneuploidy shed new light on the different mechanisms controlling meiosis in man and woman. In addition it contributes to define the role of maternal age and genetic recombination on the behavior of chromosomes during meiosis. These new data greatly contribute to our understanding of human chromosomal diseases.