Name: ______________________________KEY_______ Author Number: ________BioC 3022 section 001Day 24 Pre-class homework1. Give the function(s) encoded by each HIV gene:a. Gag core, matrix, and nucleocapsid proteinsb. Pol reverse transcriptase, integrase, proteasec. Env gp120, gp41d. Tat transactivator of transcriptione. Rev regulator of viral expression2. What host molecules are required for fusion? What viral molecules?Host: CD4 and CCR 5, Virus: gp120 and gp413. What conformational changes take place in gp120 and gp4 ?(see https://www.youtube.com/watch?v=RO8MP3wMvqg&feature=related)Gp120 changes conformation upon attachment, which allows gp41 to unfold hydrophobic tails that insert into the host cell membrane. Once inserted, gp41 refolds, bringing the virus into contact with the host cell membrane.4. Why is the low fidelity of HIV reverse transcriptase an advantage for the virus?By making frequent mistakes, RT generates lots of variants. Many are disadvantageous, but a rare few can allow the virus to escape immune or drug pressure. These variants can quickly expand to repopulate the patient.5. Why is the rev protein essential for HIV replication?Rev allows export of unspliced mRNAs from the nucleus, these unspliced mRNAs are essential because they serve as the genome for the next round of viruses.6. Why does the virus always win?Rapid replicationStrong selection for resistanceGradual loss of immune competenceLatent T-cells allow the virus to ‘hide’ for decades7. Why might a vaccine against HIV be difficult to develop?The virus mutates rapidly, so antibodies against the original virus aren’t effective. The most immunogenic parts of the viral surface proteins are not accessible to the immune system.Name: ______________________________KEY_______ Author Number: ________BioC 3022 section