1. University of Minnesota School of Public Health;2. City of Hope Comprehensive Cancer CenterBeckman Research Institute;3. McMaster University;4. University of CaliforniaSan Francisco;5. Brigham and Women's Hospital and Harvard Medical School;6. Center for Medical Ethics and Health PolicyBaylor College of Medicine;7. Mayo Clinic;8. University of Michigan Medical School;9. Data Coordinating CenterBoston University School of Public Health;10. University of Michigan School of Public Health;11. see acknowledgments for list of nonauthor members of the PGen Study Group