Current trends in mapping human genes.

The human is estimated to have at least 50,000 expressed genes (gene loci). Some information is available concerning about 5000 of these gene loci and about 1900 have been mapped, i.e., assigned to specific chromosomes (and in most instances particular chromosome regions). Progress has been achieved by a combination of physical mapping (e.g., study of somatic cell hybrids and chromosomal in situ hybridization) and genetic mapping (e.g., genetic linkage studies). New methods for both physical and genetic mapping are expanding the armamentarium. The usefulness of the mapping information is already evident; the spin-off from the Human Genome Project (HGP) begins immediately. The complete nucleotide sequence is the ultimate map of the human genome. Sequencing, although already under way for limited segments of the genome, will await further progress in gene mapping, and in particular creation of contig maps for each chromosome. Meanwhile the technology of sequencing and sequence information handling will be developed. It is argued that the HGP is a new form of coordinated, interdisciplinary science; that its primary objective must be seen as the creation of a tool for biomedical research--a source book that will be the basis of study of variation and function for a long time; that the impact on scientist training will be salutary by relieving graduate students of useless drudgery and by training scientists competent in both molecular genetics and computational science; and that the funding of the HGP will have an insignificant negative effect on science funding generally, and indeed may have a beneficial effect through economy of scale and a focusing of attention on the excitement of biology and medical science.