Wessex Reg. Genetics Centre / Wellcome Images
Down syndrome karyotype (formerly called trisomy 21 syndrome or mongolism), human male, 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 leukaemia. Older survivors often develop Alzheimer’s disease in their fourth or fifth decade. The syndrome is associated with advanced maternal age.