Caption:
Down syndrome human karyotype 47, XY, +21. This male has a full chromosome complement plus an extra chromosome 21. Symptoms include a varying degree of mental retardation, growth failure, muscular hypotoicity, flay occiput, large tongue, slanting eyes, simian palmar crease, intestinal and heart problems, and acute leukemia. Older survivors often develop Alzheimer's disease in their fourth or fifth decade. The syndrome is associated with advanced maternal age. Supplied by Wessex Reg. Genetics Centre, courtesy of Wellcome Images.