Mutagen

The significance of mutations is profoundly influenced by the distinction between germline and soma. Mutations in somatic (body) cells are not transferred to offspring. Mutations that occur in a somatic cell, in the bone marrow or liver for example, may damage the cell, make the cell cancerous or even kill the cell. Whatever the effect, the ultimate fate of that somatic mutation is to disappear when the cell in which it occurred, or its owner, dies. However, mutated DNA can only be passed to the next generation if it is present in a germ cell such as spermatozoa and ova (eggs), each of which contribute half of the DNA of the new organism. Germline mutations will be found in every cell descended from the zygote to which that mutant gamete contributed. If an adult is successfully produced, every one of its cells will contain the mutation. Included among these will be the next generation of gametes, so if the owner is able to become a parent, that mutation will pass down to yet another generation.