Learn about gene changes called mutations, how inherited mutations can lead to cancer, what types of cancer may be hereditary and how parents can pass gene mutations to their children.

How mutations are inherited

Men and women can pass an inherited gene mutation to their sons or daughters through their sperm or eggs. When a person with a gene mutation has children, each child has a 50 percent chance of inheriting the same mutation.  

Genetics experts look carefully at a family’s medical history for signs of hereditary cancer. You can assist them by gathering medical information from relatives on both sides of your family.

Typically, a genetics expert will look at three or more generations of a family’s medical history to help predict whether family members are likely to have an inherited mutation. They will use this information to create a medical family tree known as a pedigree. 

Degrees of relatedness

When speaking about a family tree, experts use the term “degree of relatedness” to describe how closely related one family member is to another. "First-degree relatives” share half of their DNA. If a person has an inherited mutation, each of their first degree relatives have a 50 percent chance of testing positive for the same mutation. Second-degree relatives share one fourth of their DNA, third-degree relatives share one eigth of their DNA, and so on. 

  • First-degree relatives
    • Siblings
    • Children
    • Parents
  • Second-degree relativesHalf-siblings
    • Uncles and aunts
    • Grandparents
    • Grandchildren
    • Nieces and nephews
  • Third-degree relatives
    • Cousins
    • Great grandparents
    • Great-aunts and Great-uncles

Picture of a sample pedigree

Last updated July 20, 2020