TIMING OF OOCYTE MATURATION IN THE MOUSE AND ITS RELEVANCE TO RADIATION-INDUCED CELL KILLING AND MUTATIONAL SENSITIVITY

Timing oocyte development by labeling the zona pellucida indicates that it takes 6 weeks (possibly a few days more) for a stage 3b oocyte to reach ovulation. Thus the shift in mutation frequency with time after irradiation occurs in an oocyte stage that is comparable in all mammals so far investigated, and in the mouse low-mutational sensitivity is not restricted to the arrested dictyate oocyte stage. Some oocytes with nuclear morphology similar to the arrested human oocytes give low mutation rates. Degree of chromosome condensation in early oocytes does not appear to be a reliable criterion of oocyte sensitivity to either cell killing or mutation induction, and generic data on mouse oocytes may be more generally applicable than commonly thought. © 1979.