How is the sea of electrons model is used to explain the physical properties of metals? electrons give off a charge, the greater or lesser the metal will depend on how packed the universe is in the metal, atoms and such.
Mutations can also be caused by exposure to specific chemicals or radiation. These agents cause the DNA to break down. This is not necessarily unnatural  even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair.
The genes affected by these mutations are known as cell-division-cycle genes, or cdc genes. Many of these mutations cause cells to arrest at a specific point in the cell cycle, suggesting that the normal gene product is required to get the cell past this point.