IONIZING-RADIATION INDUCED DNA LESIONS WHICH LEAD TO CHROMOSOMAL-ABERRATIONS

Several radio sensitive mutant cell lines of CHO and V79 cells have be en studied to explore a possible correlation between radiation induced DNA lesions and chromosomal aberrations. In the xrs mutants which are deficient in DNA double strand break (DSB) repair, there is a correla tion between the extent of the defect in repair and the frequencies of radiation induced chromosomal aberrations. In another type of radiose nsitive mutant (V-C4), which has no detectable defect in DNA DSB repai r, the frequencies of X-ray induced aberrations are high in comparison to wild type V79 cells. However, following treatment with restriction endonucleases or fission neutrons, the frequencies of aberrations are similar to those in V79, indicating that V-C4 cells are defective in repair of X-ray induced lesions other than DSBs. Though DSBs are the m ost important lesions leading to chromosomal aberrations, in repair de ficient mutants, radiation induced lesions other than DSBs can lead to chromosomal aberrations.