QnAs with David Baltimore. Interview by Prashant Nair.

A t the age of 37, David Baltimore accomplished what many researchers dream of but few achieve: reversing an entrenched dogma, eventually leading to a new view of life. In the early 1970s, Baltimore, a member of the National Academy of Sciences and a professor of biology at the California Institute of Technology, discovered reverse transcriptase—an enzyme found in some tumor viruses whose genetic code is written in the RNA alphabet. He found that reverse transcriptase can copy RNA into DNA, indicating that some viruses replicate via a DNA intermediate. The finding, which won Baltimore and others the 1975 Nobel Prize in Physiology or Medicine, enriched biologists’ views on the direction of flow of genetic information in cells. Baltimore was the keynote speaker at the Sackler Colloquium, “Telomerase and Retrotransposons: Reverse Transcriptases That Shaped Genomes,” held in September 2010.* Here, he offers PNAS readers his perspectives on reverse transcription.