DNA is the whole "map" of the human body. It is something that all humans have, and it tells the body what to do. DNA is the reason that we look like our parents, because we get some of their DNA to make our own.
People have been trying to understand the human body for a long time. In 1860, Mr. Mendel discovered why we look similar to other people in our family. It is because of small things called "genes" in our body. In 1953, two scientists, Watson and Crick, found out that those small parts are real messages. They are written in the DNA with a special language.
In 1961, another two scientists found the first "word" that they could understand in that language. It shows how DNA tells the cell （细胞） to build its parts. So far, scientists have found all the words in the DNA map, but we do not understand what they all do. By understanding what just one "word" means, we can help to save people from several illnesses. So the more we understand, the more doctors will be able to do.
Most people hope that this will help to make better medicine to help sick people. Other people worry that when we learn more "words" and find out more information, we will use it in the wrong way, just to make people more attractive, or stop sick people getting jobs.
