Spontaneous and X-ray-induced Somatic-chromosome Aberrations in the Chinese Hamster

SummaryThe spontaneous and induced chromosome-aberration rates in the bone-marrow of the Chinese hamster, Cricetulus griseus, have been investigated. The spontaneous aberration rate is so low that no aberrations have yet been seen in control material. Two hours after irradiation the induced aberration rate was 0·0051 breaks per cell per r. The aberration rate fell rapidly with time after irradiation. Aberrations of all the expected types were found, but two-hit aberrations did not appear until the sixth hour. The results support the conclusion that epithelioid cells in vitro have about the same sensitivity as a rapidly-dividing tissue in vivo, while ‘fibroblasts’ are much more sensitive.