A mutation is any random change in the DNA of a cell or an organism. DNA is a long helical molecule with all the instructions for how living things will develop. These changes can happen either through external factors, like radioactivity, or UV and x-rays, or through internal factors, such as when a cell is dividing and it incorrectly copies the DNA. DNA is the instruction book for how to make various molecular machines—proteins. Proteins make up an important aspect of our cells; they help our cells extract energy from food, do the housekeeping, and even make new proteins. These proteins and their function in the body lead to the traits that make us unique, like eye colour or our blood type. Therefore, when the DNA changes, our proteins might also change, which could lead to a change in a trait. Most of the time, mutations don't cause a significant change. These are considered neutral mutations. Sometimes, however, mutations can be good or bad. When they are bad, they lead to diseases, like cancer or cystic fibrosis. On the other hand, when they're good, it can allow an organism to more readily adapt to its environment.