Retrovirus virion, viral genome and RNA transcript. A.) Schematic diagram of virion structure. B.) The genome organisation of an oncoretrovirus provirus DNA; locations of all genes and the LTR are indicated. C.) Viral RNA transcripts. The full-length transcript serves as the RNA genome and as a messenger RNA for Gag and Gag/Pol polyproteins. The Env is translated from the spliced transcript.