What is it?
A hereditary (or germinal) mutation is one that occurs in a sexual cell (the egg or the sperm).
Because every cell in the body develops from these, if the abnormal cell survives, all the cells of the new individual carry that same mutation.
Contrary to genetic changes in non-sexual cells (called somatic mutations), a genetic change in the sexual cells is hereditary and can be passed from generation to generation.
Luckily, hereditary mutations are rare, being responsible for just 5-10% of all cancers.