Clapp was born and raised a mile outside of Marysville, Indiana and was one of 46 graduates in his rural consolidated high school class.
[1] While attending Hanover College for his undergraduate degree, Clapp spent a summer working with children with learning disabilities.
[1] During this time, he worked alongside Maureen Harrington to develop and formalize IU's medical degree and PhD track program.
[2] Clapp also focused on the genetic control of hematopoiesis with a specific interest in the role of the hematopoietic system in children with a predisposition to bone marrow failure and cancer.
[6] In October 2020, Clapp was elected a Member of the National Academy of Medicine for "work that has led to fundamental new insights into the pathogenesis of neurofibromatosis and improved lives for children and adults with this disorder.