Five of the most variable loci detected in human DNA by hybridization with DNA fingerprint probes have been cloned and characterized. Each locus consists of a tandem-repetitive minisatellite, with repeat units ranging in length from 9 to 45 base pairs depending on the locus. All of these cloned minisatellites act as locus-specific hybridization probes, and detect extremely variable Mendelian loci with heterozygosities ranging from 90 to 99%. These five hypervariable loci, together with a previously-isolated minisatellite designated pΛg3, are dispersed over four autosomes (chromosomes 1, 5, 7 and 12). Syntenic pairs on chromosomes 1 and 7 show no detectable pair-wise linkage, and thus these hypervariable loci show no evidence of clustering within the genome and should provide valuable markers for mapping inherited disease. The locus-specific minisatellites act as very sensitive hybridization probes, and can be pooled to detect several hypervariable loci simultaneously. The applications of these probes in individual identification, paternity testing and analysis of cell chimaerism are discussed, and are illustrated by an analysis of forensic specimens from two victims who had been sexually assaulted and murdered.

We are very grateful to Professor J. Dausset and Dr H. Cann at the Human Polymorphism Study Centre, Paris. for the generous provision of DNA samples from the panel of CEPH families, to Dr Mary Davis for providing DNA from the JDA hybrids, and also to the following people who kindly allowed us to use their hybrids. Dr Ellen Solomon. Dr Nigel Spurr. Dr P. Goodfellow, Dr Denise Sheer, Dr John Cowell and Dr Ben Carritt. We also thank Anabel Kearney who did the enzyme analysis on the hybrids, and Lynne West who did the karyotyping. We are also grateful to the Leicestershire Constabulary for their permission to cite details of the forensic analysis. A.J.J. is a Lister Institute Research Fellow, and this work was supported by a grant to A.J.J. from the Medical Research Council. The minisatellite probes are the subject of Patent Applications, and commercial enquiries should be addressed to the Lister Institute of Preventive Medicine, Brockley Hill, Stanmore. Middlesex, H A7 4JD, U.K.