Methods for Genetic Linkage Analyses

Reports of the mapping and cloning of genes appear regularly in the major newspapers and lay magazines. The catalog of mapped and cloned human genes is being produced biannually as the report of the Human Gene Mapping workshops. In the latest report (McAlpine et al., 1988 14 ), over 1200 genes were listed, of which half were cloned and over 2400 restriction-length polymorphic locations were identified in the human genome. The method of genetic linkage analysis goes hand in hand with the mapping of the genes and often is the key prior step in successfully mapping a locus of interest. Whereas mapping places a gene’s location on a particular chromosome (often with sufficient precision to lead to application of cloning technology) linkage analysis defines the linear order among a series of loci. For a complete discussion of mapping techniques and methodology, see the chapter by Sparkes, this volume.