Gene mapping, delineation of the genes on a cell's chromosomes, implying the identification of the complete sequence of the DNA, the material that makes up a gene. One current method of gene mapping is to isolate the DNA by cleaving the chromosome. Cleavage is achieved by the introduction of a restriction enzyme, which digests DNA at a specific recognition site. The recognition site also serves as a location marker, and by using a series of restriction enzymes, researchers can investigate a small segment of a chromosome. Other mapping techniques involve the use of radioactive DNA or RNA, which isolates a specific sequence in the gene, and molecular cloning, which allows the artificial generation of genes with a known composition. The genes of some simple organisms (like viruses) have been completely mapped. A vast project to map the human genome is now underway.
See also: Gene.