Unrepaired or improperly repaired DNA damage can lead to the accumulation of mutations in the genome. Mutations in key DNA regions controlling cell growth can initiate uncontrolled cell division. These mutations may then alter the genetic information carried by the DNA, leading to dysfunctional proteins and disease development. Cancer arises when a single cell accumulates multiple mutations in genes related to cell division, allowing it to proliferate uncontrollably and form a tumor. In cases where DNA damage is severe and cannot be repaired, cells may undergo apoptosis or enter senescence.