[Effect of 5-bromodeoxyuridine concentration on sister chromatid exchange frequency in consecutive replication cycles].

A yield of single and twin sister chromatid exchanges (SCE) in Chinese hamster cells incubated at different concentrations of 5'-bromodeoxyuridine (BrdUrd) has been studied. The ratio of SCEs formed in the second and in the first cycle has been discovered to be dependent on the dose of BrdUrd; it is 1.5:1 for the high concentration of BrdUrd and 1:1 for the lowest one. The authors arrived at a conclusion that the observed level of SCEs--0.1 per chromosome per cycle for the lowest concentration is spontaneous.