Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.|Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.|Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.|Department of Statistics, Stanford University, Stanford, CA, USA.|Department of Genome Sciences, University of Washington, WA, USA.|Department of Genome Sciences, University of Washington, WA, USA.|Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.