2. Phylogenic subgroup of HIV-2 This phylogenic tree demonstrates the multiple subgroups within the HIV-2 viral family. Horizontal branch lengths represent the relative genetic distances between each group

3. Geographic origins of HIV-2 strains HIV-2 predominantly comes from western Africa Within each subgroup of HIV-2, there are several countries from which different viral strains have originated. There is no correlation between the geographic origin of an HIV-2 isolate and its phylogenic clustering.

4. Two type of HIV (genetically and antigenically). HIV-1 - cause of the current pandemic while HIV-2 is found in west Africa but rarely elasewhere. The HIV-2 type is closely related to simian immunodeficiency virus (SIV) found in west Africa. HIV Subtypes

5. Subfamilies of retroviruses Oncoviruses: associated with the activation of certain cell genes leading to tumor development Type A Mouse intracisternal type A Type B Mouse mammary tumor virus (EUR ans USA) Type C Murine leukemia virus Human T cell leukemia virus types I and II, Bovine leukemia virus Type D Mason-Pfizer virus, SAIDS virus

6. Virus budding forth from the surface of a cell. Note how the outer mb of the virus is composed of the lipid bilayer mb of the host cell studded with integrated protein products (envelope proteins) of the virus. Viral budding