Ellen spent four years completing her PhD in industrial and chemical engineering. Now, wincing as a company doctor drew a few drops of blood for her preemployment physical, she could hardly contain her excitement about the job she'd been offered at one of the country's foremost metallurgical research institutes. Two days later the phone call came. You are perfectly healthy the young doctorsaid. But tests have revealed you harbor a gene that can result in decreased levels of a blood enzyme, glucose-6-phosphate dehydrogenase. Without the enzyme s protection, you have a slightly increased risk of developing a red blood cell disease if you come into contact with certain chemicals in our laboratory I'm sorry, he said. The job has been offered to someone else.