Avian sarcoma viruses (ASV) represent perhaps the best laboratory model for the study of viral oncogenesis. Only with ASV has the product of a single viral gene product (src) been shown to be both necessary and sufficient for cell transformation. ASV, like all retroviruses, replicates through a DNA intermediate. Therefore, understanding how these viruses synthesize their viral DNA and how that V-DNA interacts with the host cell chromosome is crucial to understand both viral gene expression and replication. The goal of this project is to characterize the different forms of V-DNA present in the infected cell using restriction endonucleases, agarose gel electrophoresis, hybridization, molecular cloning and DNA sequencing. We also hope to use similar techniques on the integrated or proviral form of viral DNA.