The Molecular Basis of Inheritance Life?s Operating Instructions * In 1953, James Watson and Francis Crick introduced an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA * Hereditary information is encoded in DNA and reproduced in all cells of the body * This DNA program directs the development of biochemical, anatomical, physiological, and (to some extent) behavioral traits * DNA is copied during DNA replication, and cells can repair their DNA Concept 16.1: DNA is the genetic material * Early in the 20th century, the identification of the molecules of inheritance loomed as a major challenge to biologists The Search for the Genetic Material: Scientific Inquiry