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.
However, these mistakes are rare, and the cell has repair mechanisms that can repair some damage. - Sometimes a permanent change occurs in a cell's DNA and this is called a mutation. - Because a mutation in a gene causes a change in the protein that is made, the enzyme is nonfunctional. Types of mutations - Mutations can range from changes in a single base pair in the coding sequence of DNA to the deletions of large pieces of chromosomes. - Point mutations involve a chemical change in just one base pair and can be enough to cause a genetic disorder. - A point mutation in which one base is exchanged for another is called a substitution. - Most substitutions are missense mutations, where the DNA code is altered so that it codes for the wrong amino acid. - Other substitutions, called nonsense mutations, change the codon for an amino acid to a stop codon. Nonsense mutations cause translation to terminate early. Nearly all nonsense mutations lead to proteins that cannot function normally. - Another type of mutation that can occur involves the gain or loss of a nucleotide in the DNA sequence.