Department of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USADepartment of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USA.|Department of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USADepartment of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USA.|Department of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USA.|Department of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USADepartment of Human Genetics and Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA and Department of Biology, Spelman College, Atlanta, GA 30314, USA.