DETECTION OF DNA-DAMAGE INDUCED BY LOW AN D HIGH TEL IONIZING-RADIATIONS

Ionizing radiations induce DNA damage mainly via hydroxyl radicals pro duced by radiolysis of water. The most currently studied DNA lesions a re single and double strand breaks. By mean of plasmid relaxation coup led or not with the use of specific DNA repair enzymes, wee were able to show that base damage are also produced, in addition to DNA strand breaks, in plasmid DNA irradiated in solution with gamma rays of Co-60 . When DNA is it-radiated in a dry state, doses 100 fold higher are ne cessary to produce similar levels of damage. Preliminary results obtai ned with accelerated heavy ions show the importance of the induction o f double strand breaks.