NEW YORK (AP) — Scientists say they've found a new way to help determine whether specific genetic abnormalities are likely to make people sick, a step toward avoiding a vexing uncertainty that can surround DNA test results.

Researchers used genetic engineering to create thousands of tiny variations in a gene linked to breast cancer, and tested each one in a lab to predict whether it would promote the disease if it appeared in a person.

When those predictions were checked against what scientists already knew about the BRCA1 gene, "we were very accurate," said Lea Starita of the Brotman Baty Ins...