PCC technique reveals severe chromatin lesions and repair in G2-arrested cells after alpha irradiation

Exponentially growing Chinese hamster V79 cells were exposed to 4 MeV alpha particles emitted by an americium-241 source. The chromatin of cells arrested in G2 by alpha irradiation is severely damaged, though all cells were still capable to condensate their chromatin after fusion with mitotic cells. In addition to the common types of aberrations (breaks, gaps, dicentrics and exchanges) cells were found possessing one or more chromosomes with long stretches of undercondensed chromatin. Repair of these lesions was indicated by site-specific unscheduled DNA synthesis and by the observation that condensation of these regions improved during G2 arrest.