Gene mapping and medical genetics

Human chromosome 8 is perhaps best known for its involvement in Burkitt's lymphoma and as the location of the tissue plasminogen activator gene, PLAT, which has been genetically engineered to provide a natural fibrinolytic product for emergency use in cardiac disease. Since chromosome 8 represents about 5% of the human genome, we may expect it to carry about 5% of human gene loci. This would correspond to about 90 of the fully validated phenotypes in the MIM7 catalogue.' The 27 genes assigned to chromosome 8 at the Ninth Human Gene Mapping Workshop (Paris, September 1987) thus represent a third of the expected number. In addition, six loci corresponding to fragile sites, three pseudogenes, and four gene-like sequences were reported.2 Nevertheless, this is but a small fraction of the 500 to 5000 gene loci expected from a genome that contains between 10 000 and 100 000 genes.