DAMAGED CHROMATIN DOES NOT PREVENT THE EXIT FROM METAPHASE-I IN FUSEDMOUSE OOCYTES

The presence of checkpoint mechanisms which are able to recognize dama ged chromatin and thereafter to prevent exit from metaphase I has been investigated in giant mouse oocytes produced by fusion of a normal me taphase I oocyte with an equivalent oocyte with damaged chromatin. The presence of damaged chromatin did not prevent the onset of anaphase I in both sets of chromatin in the fused cells. Interestingly, fused or unfused cells containing only damaged chromatin failed to enter anaph ase and persisted instead in a metaphase-like state. These results dem onstrate the fragility of checkpoint controls in mammalian female germ cells.