DNA double-strand break induction in yeast by X-rays and α-particles measured by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis was used to separate chromosomes of Saccharomyces cerevisiae 211 *B after irradiation with X-rays and α-particles. After electrophoresis, gels were stained with ethidium bromide, placed on a UV-transilluminator and photographed with a digitizing camera connected to a personal computer. Linearity between DNA amount and fluorescence was demonstrated. Fluoroescence intensity for the band with the lowest electrophoretic mobility was found to decrease exponentially with dose. Based on the known size of the native DNA molecules, double-strand break yields were found to be (8.2 ± 0.4) and (14.8 ± 0.5)10-12 (g/mol)-1Gy-1 for 80 keV X-rays and 3.5 MeV 241Am α-particles respectively which gives a relative biological effectiveness of 1.8 ± 0.1. (author)