Department of Mathematics, The Ohio State University, Columbus, Ohio, United States of America.|Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.|Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.|Department of Mathematics, The Ohio State University, Columbus, Ohio, United States of America.|Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.