Cell-cycle checkpoint kinases: checking in on the cell cycle

In response to DNA damage, cell-cycle checkpoints integrate cell-cycle control with DNA repair. The idea that checkpoint controls are an integral component of normal cell-cycle progression has arisen as a result of studies in Drosophila and mice, in addition, an appreciation that DNA damage arises as a natural consequence of cellular metabolism, including DNA replication itself, has influenced thinking regarding the nature of checkpoint pathways.