DNA repair is a crucial process in cell biology. Failure to repair DNA prior to cell division can result in abnormal chromosome numbers and high numbers of mutations characteristic of cancer cells. Cells have several checkpoints during the cell cycle to ensure that cells with extensively damaged DNA undergo apoptosis rather than cell division. Those cells where the damage can be repaired must do so prior to cell division. DNA repair mechanisms are spatially and temporally regulated within the cell to ensure that enzymes for repair are recruited to the correct areas.