[Possible mechanisms of the emergence of chromosome aberrations. VIII. Cytogenetic analysis of the dynamics of repair and occurrence of potential chromosome damage in bone marrow cells of gamma-irradiated mice].

The dynamics of mitosis delay and appearance of structural chromosomal aberrations (SCA) in relation to radiation dose and time after postradiation are studied. The results obtained suggest that potential DNA damage (PD)--chemical modifications responsible for SCA formation--induce a G2-block. According to this result, it was concluded that PD arose in 30, 80, 90, and 95% of cells at radiation doses of 9, 24, 51, and 75 cGy, respectively. In cycling cells, PD are either repaired or become SCA. If within the first hour after radiation, it was more probable that they would be repaired. The rate of PD repair decreased and the probability of SCA increased as the length of time after radiation increased. The probability of PD also depended on the separation rate of sister chromatids in mitosis. Radiation affects the rate of chromatid separation and, consequently, the occurrence of PD.