Heavy ion-induced DNA double-strand breaks in yeast

DNA double-strand break (dsb) induction in diploid yeast was measured by neutral sucrose sedimentation after exposure to very heavy ions with values of linear energy transfer (LET) ranging from about 300 to 11500 ke V/microns. Linear fluence dependencies were found in all cases from which dsb production cross-sections (sigma dsb) could be calculated. Corresponding cross-sections for cell killing (sigma i) were derived from final slopes of survival curves measured in parallel and for the same fluence range. A close correlation was found between sigma i and sigma dsb. It is calculated that over the entire LET range, including 30 MeV electron irradiation, about 22 dsb are induced per lethal event when high exposures are considered.