Anaphase is not the point of no return, say Qinghua Shi and Randall King (Harvard Medical School, Boston, MA). If cells make errors in anaphase chromosome segregation, they mount a rescue operation. The final stages of cytokinesis shut down, producing tetraploid cells that might even be able to regenerate functional diploid cells.
Shi and King started out looking for different chromosome missegregation rates in various cell lines. They noticed that the rate of missegregation was 45–166-fold higher in spontaneously arising binucleated cells than in cells with normal divisions. In time-lapse experiments, these aberrant cells did not delay in mitosis but reversed their division process just before cytokinesis completion. The thin, remaining bridge between dividing cells opened back up, yielding a binucleate cell.
Extrapolating from experiments using probes for four chromosomes, it is likely that there is a segregation error during virtually all divisions that produce...
