The CHEK2 gene is responsible for making a tumor suppressing protein that regulates how rapidly a cell can divide. When DNA is damaged, CHEK2, along with other proteins, come in and stop division of that cell. When the CHEK2 gene is mutated, it cannot complete this important task. As a result, cancer risk increases, particularly breast and colon cancer. The NCCN recommends that those who have a mutation should have a yearly mammogram and colonoscopy every five years beginning at age 40 or 10 years prior to the earliest diagnosis in the family. The CHEK2 mutation is inherited in an autosomal dominant manner, meaning each first degree relative (parent, child, and sibling) of an individual with this condition has a 50% chance of inheriting the disease causing mutation.