Mutations are changes in DNA which happen naturally and are the basis for evolution. A mutation occurs when DNA polymerase makes a mistake when copying the DNA strand during cell division, resulting in a slight change in the DNA of the newly created cell. When a cell divides (during a process called meiosis), the DNA in the original cell must make a copy of itself for the new cell. It does this through a process known as DNA replication. During DNA replication, an enzyme known as DNA polymerase makes a copy of the DNA using the original DNA strand as a template. Although this process is usually very accurate and results in an exact replica of the original DNA, on occasion, the DNA polymerase may miscopy a section of the DNA, resulting in a slight change in the newly formed DNA strand. This is called a mutation and although mutations do not occur frequently, they are an important part of evolution and occur naturally.