Next time you're at a family gathering, notice if there are any striking patterns. The way you look is determined by genes, which hold the instructions our bodies use to make our features. Which genes the baby gets from each parent is random, like flipping a coin. Genes also hold information that causes diseases. These diseases are called genetic, or inherited, diseases.
Cystic fibrosis is an example of a genetic disease.
Some genetic diseases don't show up until later in life, even though the genes are present from birth. Genes may play a part in the changes in your body when you become a teenager, as well as the normal changes that happen as people grow older. As people get older, they may have trouble with eyesight and hearing and their senses of taste and smell may not be as sharp. Older people may slow down physically, and their memories may not be quite as sharp. But people over the age of 70 still have hobbies and interests, play sports, make jokes.