Genes play a role in causing other conditions that seem to "run in families," too, though not in as clear a way. Problems like diabetes, heart disease, and asthma often are caused when several genes interact with each other and with the environment in certain ways. These are called susceptibility genes. They do not cause a disease by themselves, but make a person more prone to develop the disease if other factors (like smoking, weighing too much or being exposed to toxic chemicals) are present, too. Scientists can use the knowledge they're gaining about these genes to help predict what diseases a person is likely to have in his or her lifetime. This may mean that people can make changes in their lives to help prevent the disease before it happens - a good thing!

The things that scientists are learning about genes and how they affect us will make a difference in your life and an even bigger difference in the lives of your children. Understanding more about the genes that play a role in diseases and in how we respond to medicines will help scientists and doctors predict the health problems we're most likely to have, diagnose them earlier and more accurately, develop new medicines to treat them more safely and effectively, and maybe even prevent them. If you think this is exciting work, maybe you'll decide to play a role in it by studying hard and becoming a scientist, doctor, nurse or genetic counselor yourself!