Deadly genetic defects often involve single- nucleotide polymorphisms—single changes in the base pairs that make up DNA. As a graduate student at Johns Hopkins University, Steven Laken discovered that such a change occurs in six percent of Ashkenazi Jews and correlates with a 20 to 30 percent risk of colon cancer. With 20 million Ashkenazi Jews potentially at risk, Laken was not satisfied with simply finding the defect; he wanted to devise a rapid test for it. He created a lab procedure that separates DNA into fragments and then uses mass spectrometry to quickly search the fragments for the polymorphism. Doctors are now using the technique to screen patients with Ashkenazi backgrounds for colon cancer. After completing his graduate work, Laken joined Maynard, MA-based Exact Sciences, where he is now adapting the innovation for broader genetic tests, including one for nonpolyposis colon cancer, the most common inherited form of the disease. Laken believes his methods could spot virtually any illness with a genetic component, from asthma to heart disease.