Department of Genetic Medicine and Development, University of Geneva Medical School and University Hospitals of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland. Stylianos.Antonarakis@medecine.unige.ch
The sequence of chromosome 21 was a turning point for the understanding of Down syndrome. Comparative genomics is beginning to identify the functional components of the chromosome and that in turn will set the stage for the functional characterization of the sequences. Animal models combined with genome-wide analytical methods have proved indispensable for unravelling the mysteries of gene dosage imbalance.