Thought to result from mixing of different virus strains in same cell, recombination of surface protein genes to give new arrangements. Vaccines not good for more than a few years because of new strains. Enough DNA to code for about 70 proteins. DNA synthesis occurs in nucleus. Proteins synthesized in cytoplasm, travel back to nucleus for assembly.
Virions bud through inner membrane of nucleus to outside of cell.
See Section 8.21. RNA could serve as mRNA but doesn't. Instead, travels to nucleus. Animation showing penetration of HIV . Animation showing the action of reverse transcriptase .