| Modification Notes |
An extra copy of chromosome 21, the smallest human autosome chromosome, results in Down syndrome. Down syndrome is a genetic disorder characterized by congenital heart abnormalities and mental retardation. The Down syn-drome critical region (DSCR) maps specifically to chromosme 21q22.13 and includes several genes which are likely associated with the pathogenesis of Down syndrome. Symptoms of Down syndrome include abnormal neuronal differentiation and elevated apoptosis in the developing brain. DSCR9 (Down syndrome critical region protein 9) is an 149 amino acid protein preferentially expressed in testis. The genes encoding DSCR10 and DSCR9 are not present in mice, suggesting that these genes have emerged during evolution in the primate lineage. |