Mutations affect organisms in two different ways. Genetic mutations are inherited DNA changes that can be passed on to the next generation. Somatic mutations are DNA changes that are acquired after birth. Mutations can be helpful, harmful or make no difference at all.
Genetic mutations are responsible for evolution. They occur in reproductive cells (eggs and sperm) and are also called germ line mutations. These changes affect every body cell and last a lifetime.
Some mutations are beneficial, such as when a mutation gives a moth a color that better blends with its environment and enables it to avoid predatory birds. Sometimes a mutation is harmless, such as was the case with Ernest Hemingway’s cats that were born with extra toes. However, mutations can cause serious disorders such as hemophilia, cerebral palsy, Huntington’s disease and many others.
Somatic mutations are acquired after birth in non-reproductive cells. These changes occur in only certain cells of the body and can be caused by tobacco use, ultraviolet radiation, viruses, chemicals and age. Acquired mutations are the most common cause of cancer.
Humans experience many somatic mutations over a lifetime, and the human body is normally able to correct most of these changes. This is why there is only a small chance of one mutation causing cancer. It normally takes many mutations over a lifetime to cause cancer. This is why older people are the most likely group to get cancer, as they have had more chances for mutations to build up.