Vincent, Dickson, Rich, and Alan review the 100 year old finding by Peyton Rous of a transmissible sarcoma of chickens, a discovery that ushered in the era of tumor virology.

Vincent and Dickson continue virology 101 with a discussion of information flow from RNA to DNA, a process known as reverse transcription, which occurs in cells infected with retroviruses, hepatitis B virus, cauliflower mosaic virus, foamy viruses, and even in uninfected cells.