Experimental Evidence for Hysteresis in the Cell Cycles of Xenopus Laevis Egg Extracts

............................................................................... ii ACKNOWLEDGMENTS............................................................... iv TABLE OF CONTENTS................................................................ vi LIST OF FIGURES....................................................................... ix LIST OF TABLES........................................................................ xi Chapter 1: INTRODUCTION.......................................................... 1 1.1 The Novak-Tyson mathematical model.................................... 1 1.2 Physiology of embryonic cell cycles........................................ 2 1.2.1 Oocytes.................................................................. 2 1.2.2 Fertilized eggs......................................................... 2 1.2.3 Egg extracts............................................................ 4 1.3 Molecular mechanisms of embryonic cell cycles......................... 5 1.3.1 MPF and its function................................................. 5 1.3.2 How is MPF activity regulated..................................... 6 1.3.3 Cyclin B level and MPF activity.................................... 9 1.3.3.1 Activation threshold concentration of cyclin B and lag time........................................................ 9 1.3.3.2 Inactivation threshold concentration of cyclin B...... 10 1.3.3.3 Threshold concentration of cyclin B when a DNA replication checkpoint in engaged..................... 11 Chapter 2: BISTABILITY and HYSTERESIS....................................... 13