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.
Mutations in the DNA of body cells cannot affect the individual in which they happen. A mutation in the DNA of a body cell can cause the cell to produce a protein that does not function. A mutation in the DNA of a gamete affects the body cells of the individual that produced the gamete. Mutations in the DNA of body cells can cause the offspring to produce a protein that does not function.