Interchromosomal distribution of gamma ray-induced chromatid aberrations in Chinese hamster ovary cells*

Interchromosomal distributions of breakpoints from chromatidtype aberrations induced by gamma rays in Chinese hamster ovary (CHO) cells were analyzed. In most chromosomes the distribution was as expected from chromosome lengths for simple breaks or the respective relative corrected length in case of exchanges. There were deviations from expectation in a few chromosomes for chromatid breaks, interchanges, intra-arm intrachanges and inter-arm intrachanges. Especially interesting are the results concerning chromosomes 2 and 8, which were more often involved in exchanges than expected. An “exchange phenotype” for these chromosomes is proposed and possible explanations for the nonrandom distribution of chromosome breakpoints are presented. 1072 Martínez-López et al. The initial lesions induced by low LET radiation are probably randomly distributed throughout the chromosomal complement (Savage, 1993). A deviation of observed breakpoint localization from a random pattern may therefore rather be a result of differential repair (Pantelias, 1994). In this paper we show that not only the intrabut also the interchromosomal distribution of observed breakpoints in chromatid-type aberrations do not appear to be random in CHO cells. MATERIAL AND METHODS