LOH involving loci flanking D3S1611(MLH1) and D7S517 (PMS2) in ALL patient 74. Genomic DNA was PCR-amplified for microsatellites D3S1561, D3S1298, D7S531, and D7S503, as reported in Materials and Methods. R, remission; Rel, relapse. A schematic chromosome map indicating the location of the markers used and their approximate distances in centimorgans is also shown.28 Marker D7S481 was not informative in patient 74 (data not shown).