David Baltimore

David Baltimore (born 1938) is an American biologist who shared the 1975 Nobel Prize in Physiology or Medicine for discovering reverse transcriptase, the enzyme that copies RNA into DNA. He also devised the Baltimore classification of viruses.

According to the prevailing idea of the time, information flowed from DNA to RNA to protein and never backward. In 1970, Baltimore, working with RNA tumor viruses at MIT, and Howard Temin, working independently in Wisconsin, found an enzyme in these viruses that makes DNA from an RNA template. It showed how retroviruses, including HIV, copy their genomes, and it forced a revision of the central dogma. The two shared the prize with Renato Dulbecco.

In 1971 he proposed sorting viruses into groups by the way each makes messenger RNA, giving seven classes today. They include DNA viruses, double-stranded RNA viruses, positive- and negative-sense RNA viruses, and viruses that use reverse transcription. The scheme is used alongside the formal ranks of the International Committee on Taxonomy of Viruses.

Baltimore's group also helped to discover the RAG genes that assemble antibody genes and the transcription factor NF-κB. He founded the Whitehead Institute at age 37, was president of Rockefeller University and then of the California Institute of Technology (1997 to 2006), and was prominent in debates over the safety of recombinant DNA research and of AIDS policy. He is a leading figure in the history of molecular biology.

• Reverse Transcriptase — the enzyme he discovered
• Retroviruses — the viruses that use it
• RNA Virus — a class in his system