DNA damage occurs at a rate of 10,000 to 1,000,000 molecular lesions per cell each day as a result of environmental influences and normal metabolic activities within the cell.
While this accounts for just 0.000165 percent of the human genome's nearly 6 billion bases, unrepaired lesions in essential genes can impair a cell's capacity to function, significantly increasing the chance of tumor development and contributing to tumor heterogeneity.
The great majority of DNA damage affects the main structure of the double helix, meaning that the bases themselves are chemically altered.
These alterations, in turn, can disturb the normal helical structure of the molecules by adding non-native chemical bonds or bulky adducts that do not fit in the usual double helix.
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