Mutations
Remember how DNA is like a ladder? And how the nucleotides fit together like puzzle pieces? When a pair of puzzle pieces is missing or added, the ladder changes. This is called a mutation.
When the ladder changes, your genes do not do the right job in your body.
Most mutations occur as your body cells divide. Mutations occur naturally and in everyone. These are usually not harmful to you.
However, some mutations are harmful and can cause disease. Cancer is an example of such a disease.
