The growth and reproduction of all living organisms are dependent on the cell cycle, the process which leads to cell division.  Uncontrolled division of cells is important for disease particularly cancer.  Two events, S-phase and mitosis, are common to all cell cycles and are necessary for the two newly divided cells to receive a full complement of genes.  The onset of S-phase and mitosis are controlled by cyclin dependent kinases (CDLKs) in all eukaryotes studied from yeast to human beings.  Checkpoints controls operate which block cell cycle progression if DNA is damaged or incompletely replicated which work through the CDKs and have been implicated in the development of cancer.