Genes responsible for transformation by avian RNA tumor viruses.

Avian sarcoma viruses probably contain 4 genes. One of these, src, controls the process of transformation of the infected cell and has been located near the 3' end of the viral genome. The remaining 3 genes direct the synthesis of virion proteins: env (envelope proteins), pol (polymerase), and gag (internal proteins). They are probably in the order gag-poly-env-src. A scheme for the replication of these viruses is proposed, and several possible mechanisms for their origin and variability are discussed.