Cloning a selected fragment from a human DNA 'fingerprint': isolation of an extremely polymorphic minisatellite.

A large hypervariable DNA fragment from a human DNA fingerprint was purified by preparative gel electrophoresis and molecular cloning. The cloned fragment contained a 6.3 kb long minisatellite consisting of multiple copies of a 37 bp repeat unit. Each repeat contained an 11 bp copy of the "core" sequences, a putative recombination signal in human DNA. The cloned minisatellite hybridized to a single locus in the human genome. This locus is extremely polymorphic, with at least 77 different alleles containing 14 to 525 repeat units per allele being resolved in a sample of 79 individuals. All alleles except the shortest are rare and the resulting heterozygosity is very high (approximately 97%). Cloned minisatellites should therefore provide a panel of extremely informative locus-specific probes ideal for linkage analysis in man.