In three generations of Johnson women, only two have never gotten breast cancer.
"My aunt was diagnosed twice, then my middle sister, and she was diagnosed twice," said Paulette Johnson, a breast cancer survivor.
The University of North Carolina's Kristy Lee collects pedigree information, or family information, combined with blood and DNA. This tool may identify the genetic building block that flips on the Johnson's breast cancer switch.
"These tragic stories of cancer in a family can be caused by a single change in one of those building blocks," said Dr. Jim Evans, director of UNC Clinical Cancer Genetics Services.
Experts say rare and less common gene variants may cause inherited risk for some diseases. Researchers have identified over 100 families whose pedigree suggests a link to cancer.
Women with these genetic mutations are put at an 85 percent risk of developing breast cancer sometime in their life compared to the 10 to 12 percent risk in the rest of the population. If that specific mutation is found, scientists could test and ID at-risk folks before they get sick.
"There have been eight mastectomies. I don't want them to go through that," said Johnson.
So she and her family are teaming-up to untangle their genetic mystery for the next generation.
"If we can just be part of finding this, it would be so wonderful," said Johnson.
If you're not in a study, the cost for decoding your entire genome is about $50,000, but experts predict it could drop to $4,000 someday soon.