DNA replication is a key event in the cell cycle. Althoughour knowledge is far from complete and many elusiveregulatory mechanisms still remain beyondour grasp, manyenzymes and a multiplicity of biochemical mechanismsinvolved have been discovered. Recent findings in E. colihave confirmed and yet surpassed the original hypothesis ofF. Jacob. In yeast and higher eucaryotes, the apparentredundancy in putative origins and initiators has made anestimation...