Gene mapping refers to one of two different ways of definitively locating the gene on a chromosome. The first type of gene mapping is also called genetic mapping. Genetic mapping refers to the use of linkage analysis to determine how two genes on a chromosome relate in their positions. Physical mapping, the other type of gene mapping, locates genes by their absolute positions on a chromosome using any technique available. Once a gene is located, it can be cloned, its DNA sequence determined, and its molecular product studied.