Origin of araC-induced endoreduplicated cells

To investigate the origin of endoreduplicated cells induced by DNA-synthesis inhibitors, V79 Chinese hamster cells were treated with 1-beta-D-arabinofuranosylcytosine (araC). During the treatment, BrUdR was present in the culture medium. If endoreduplicated cells originate from cells which have undergone rereplication of DNA segments randomly distributed over the genome during araC treatment, the diplochromosomes should exhibit lightly stained bands. The data indicate that endoreduplicated cells originate from cells blocked at the G2 stage of the cell cycle rather than from cells which have undergone an aberrant rereplication during araC treatment.