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ORGANIZATION AND REPLICATION ACTIVITY OF THE MITOCHONDRIAL MASS OF OOGONIA AND PREVITELLOGENIC OOCYTES IN XENOPUS LAEVIS

The origin of the mitochondrial mass, previously well characterized in Xenupus diplotene oocytes, has been traced up to oogonia by means of electron microscopy. A polarized organization of the oogonia and of the oocytes of the succeeding stages was observed. The mitochondrial cloud was found to be built up in the centriolar region near the site where the chromosomes will be implanted along the nuclear envelope at the “bouquet” stage. Autoradiographic studies of thymidine incorporation into mitochondrial DNA suggest that mitochondrial DNA synthesis is active throughout this early period of oogenesis.