A screening technique for any of several mutations known to cluster in a relatively small number of sites (hot spots) in a gene, especially microsatellites. Simultaneous PCR reactions with several restriction fragments and the same number of pairs of primers designed to flank the deletion-prone hot spots give as many amplified fragments when normal cells or tissues are scanned, but a mutant will lack one of the restriction fragments. As the fragments sort into clusters of closely similar sizes, there is no overlap of fragments due to restriction at different sites.