[The human genome--chromosome 21]

The 21st chromosome is probably known above all in conjunction with congenital or hereditary trisomy causing Down's syndrome. Its prevalence can be to a certain extent regulated by prevention, planned parenthood and examination during pregnancy. Particularly urgent for contemporary health services, more so in countries with a high mean age, are diseases such as e.g. Alzheimer's dementia, the AD1 locus of which is assumed to be on the 21st chromosome. The locus of the APP precursor of the protein beta-amyloid is suspected, as there in patients from affected families mutational changes were found. That a casual relationship could be involved is suggested also by results obtained in transgenic mice. As to other loci of the 21st chromosome, the author mentions aldo ALS1 for amyotrophic lateral sclerosis and EPMI for progressive myoclonic epilepsy.