McGill administrators knew they had a prodigy on their hands when they were forced to make 15-year-old Colin MacLeod wait a year before starting medical school due to age restrictions. The Nova Scotian, who had already skipped three grades, spent the year teaching elementary school, and then took up his scholarship place on the pre-med program at the University. He also at the same time held down the job of managing editor of the student newspaper, and played on the varsity ice hockey team. He received his medical degree in 1932.
MacLeod’s early research focused on the causes of pneumonia and the development of serums to treat it, and he later became chairman of the department of microbiology at New York University. Throughout his career, MacLeod worked with a number of government agencies, including many years as White House advisor to Presidents John F. Kennedy and Lyndon Johnson in his role as the first ever Deputy Director of the Office of Science and Technology.
But it is for his research on the role of deoxyribonucleic acid (DNA) in bacteria that MacLeod is hailed. Alongside colleagues Oswald Avery and Maclyn McCarty, MacLeod conducted experiments on bacterial transformation which indicated for the first time that DNA was the active agent of genetic transformation in bacterial cells. Prior to the work of Avery, MacLeod, and McCarty, the genetic material was thought to be protein.
For this discovery, and the years of pioneering research that followed, Dr. MacLeod is recognized as one of the founders of molecular biology. His claims that DNA is the hereditary material in cells was not instantly embraced by the scientific community, but his revolutionary work changed the world of biology, and MacLeod was eventually honored by election to the National Academy of Sciences, the America Philosophical Society, and the American Academy of Arts and Sciences.