[Frequency of aberrations in uni- and biliary 5-bromodeoxyuridine-substituted chromatids]

Chinese hamster cells and human lymphocytes were incubated with BrdUrd during two cycles of replication and stained using the "harlequine" technique. The G2 cells were irradiated with 1 Gy of gamma-rays from the 60 Co source. The frequency of breaks in light (i.e. bifiliary substituted) chromatids was significantly lower, as compared with dark (i.e. unifiliary substituted) ones. The comparison of these data with the previously published suggests that the relative frequency of breaks in uni- and bifiliary substituted chromatids depends on the energy of quanta. A hypothesis is discussed that a resonance absorption of energy by Br atoms and an increased interaction between BrdUrd-substituted structures, which favours the repair of double-strand breaks, can explain the noted regularity.