Analysis of gamma-ray and neutron-induced chromosome aberrations in CHO-K1 cells using the atomic force microscope

THE ENUMERATION OF CHROMOSOME aberrations remains a popular method to relate DNA damage to radiation dose delivered, and is the basis of efforts to improve aberration assays. In the work reported here, atomic force microscopy was used to study the induction of chromosome aberrations in CHO-K1 cells, after irradiation with 1-3 Gy p(66)/Be neutrons and 2-7 Gy Co-60 gamma-rays. The investigation showed that small structures, not normally well defined using conventional microscopy, can be resolved and identified with the atomic force microscope. Furthermore, the height information gathered by atomic force microscopy is useful for eliminating counting mistakes, which might be caused by chromatid or chromosome overlaps. The superior resolution of atomic force microscopy over conventional optical microscopy renders the scoring of as few as 20 cells per dose point as sufficient to draw accurate dose curves that correctly express the biological damage induced by different radiation sources.