Even if you were born with healthy genes, some of them can become changed (mutated) over the
course of your life. These acquired mutations cause most cases of cancer. Some acquired
mutations can be caused by things that we are exposed to in our environment, including cigarette
smoke, radiation, hormones, and diet. Other mutations have no clear cause, and seem to occur
randomly as the cells divide. In order for a cell to divide to make 2 new cells, it has to copy all of its DNA. With so much DNA, sometimes mistakes are made in the new copy (like typos). This
leads to DNA changes (mutations). Every time a cell divides, it is another opportunity for
mutations to occur. The numbers of gene mutations build up over time, which is why we have a
higher risk of cancer as we get older.