Researchers have long known that complex diseases such as cancer and heart disease have genetic components that heavily affect their onset, progression, and response to treatment. But because these conditions involve many different genes interacting with each other as well as with factors in a person's environment, teasing out these elements has been difficult.
A newly completed map that plots where small genetic differences can exist among people may be a powerful tool for figuring out why some individuals get certain diseases and even for custom designing treatments.
Each person's DNA is composed of enormous sequences of four building blocks that go by the letters A, T, G, and C. The vast majority of these sequences are the same in all people, but about 0.1 percent of these letters differ from person to person and can affect an individual's risk of disease or response to drugs.
A common type of variation is a trade of one letter for another, known as a single-nu