A few years ago, Affymetrix’s executives faced a dilemma. Another company had asked the California firm to create a DNA chip to test for a mutation in a gene that predisposes a small percentage of people to a form of cancer. It was a good business opportunity, recalls Thane Kreiner, vice president for operations and corporate communications. One problem: Affymetrix’s ethics advisory board knew that no helpful treatment existed for anyone who tested positive. The company declined to make the chip.