What are chromosome disorders?
• Other links: Introduction to chromosome abnormalities at CDO (English) and a translation in German at Leona eV. (from: An introduction on chromosome disorders, presentation at the conference of European Chromosome 11q Network, 1998, Ede-Lunteren, Netherlands, by Dr. Conny van Ravenswaaij, Klinisch Genetisch Centrum St Radboud ziekenhuis, Nijmegen, Netherlands.) Disorders in the number of chromosomes If a pair of chromosomes consists of three in stead of two, it is named trisomy. The most general is trisomy 21 (Down syndrome) or a trisomy of the sex chromosomes (XXX, XXY or XYY). Also a trisomy of chromosome 13 or 18 can occur, but these are much more rare. A trisomy of one of the other chromosomes is rarely viable and causes spontaneous miscarriages. If one of the chromosomes is only present once it is called monosomy. A monosomy in all body cells is mostly not viable except for monosomy of the X-chromosome (Turner syndrome). If only a par of the cells shows a disorder in chromosome
