Colon cancer risk traced to common ancestor

Because the family was Mormon, the researchers were able to mine a wealth of genealogical information taken from detailed church records over the years that is now part of a large genetics database in Utah, Neklason said.

While most of the records in the study related to the Utah part of the family, the researchers eventually identified the New York branch as well.

"We just know about these two branches of the family," Neklason said. "The significance of it going so far back is there are probably many branches of the family out there that aren't aware of the mutation."

In the study, the team identified the mutation that causes a condition called attenuated familial adenomatous polyposis (AFAP), which makes people more prone to developing polyps that can cause colon cancer.

Without proper treatment, people with this mutation have a greater than 2 in 3 risk of developing colon cancer by age 80, compared to about 1 in 24 for the general population. Early treatment, however, can just about eliminate this risk.

"This study highlights that you need to pay attention to your family history," Neklason said. "With intervention to remove the polyps, the risk goes to near nothing."

(Reporting by Michael Kahn; Editing by Janet Lawrence)