Another way a child can have an unexpected trait is when a mutation occurs. Mutations are changes in the DNA. They sometimes happen for no reason we can find, and sometimes they happen because we (or our mothers while they're pregnant with us) are exposed to something in the environment (like cigarette smoke or certain chemicals) that makes the DNA more likely to change, or mutate. Most mutations are neutral - they don't hurt us or help us, and we may not even know they've happened. Some mutations are harmful, though, and can make us more prone to certain diseases or other problems.

Our cells have repair kits to fix most mutations and keep them from affecting us, but sometimes the repair kits don't work as well as they should. You can help keep your DNA repair kit working by taking good care of yourself: eat a balanced, healthy diet with lots of fresh fruits and vegetables; avoid cigarettes and other things that we know are harmful; wear sunscreen when you're outside; exercise regularly; maintain a healthy weight for your age and height; get enough sleep at night; keep a good balance between school, work and fun; and see your health care provider for regular check-ups.