As we age, our bodies inevitably deteriorate. Some changes, like grey hair and wrinkles, are easily visible. Others, like high blood pressure, often go unnoticed, but can be deadly.Just as our body shows signs of ageing, so does our genome. Damage comes from chemical reactions that alter our DNA, and from errors introduced when it is copied. Our cells protect against these ravages, but these mechanisms are not foolproof and cells gradually accumulate DNA damage over a lifetime.As a consequence of this damage, your genome is not the same in every cell; you are a patchwork of cells with subtle differences in their DNA. When a cell divides it will pass on these changes, and as they accumulate there is more and more likelihood that there will be consequences.If these changes we call them mutations chip away at the systems that govern cell proliferation and survival, this can lead to cancer.