For MEF with DSBs induced by gamma irradiation, hotspots included (a) a mouse chromosome 6 deletion hotspot shared by Mlh1−/−, Pms2−/−, Mlh3−/− and Mlh3−/−;Pms2−/− MEFs, (b) mouse chromosome 7 deletion hotspot shared by Mlh1−/−, Pms2−/−, Mlh3−/− and Mlh3−/−;Pms2−/− MEFs that we had been previously identified in Mlh3−/−;Pms2−/− deficient intestinal adenocarcinomas but not matched normal mucosa or Mlh3−/− adenomas [10] and (c) a mouse chromosome 12 amplification hotspot in Mlh1−/− MEFs, also previously seen in Mlh3−/−;Pms2−/− deficient intestinal adenocarcinomas [10]. This evidence concerns the gene MLH1 and adenoma.