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Unformatted text preview: Biology 180: Week 6 study questions Autumn 2007 1. To complete their life cycle, viruses have to enter a cell. What is required for an enveloped virus to enter a cell? Proteins in the viral envelope have to bind to specific proteins on the host cell membrane. After binding, the envelope and membrane fuse so the capsid can enter the host cell. Describe a drug that would prevent an enveloped virus from entering a cell. A molecule that binds to the protein in the viral envelope or to the protein in the host cell membrane would prevent the protein-protein interaction and inhibit entry. 2. To complete their life cycle, viruses have replicate their genomes. What is required for an RNA virus like HIV to replicate its genome? The enzyme reverse transcriptase has to make a DNA version of the viral genome, which is then inserted into a host cell chromosome so it can be copied. Describe a drug that would prevent a virus like this from replicating its genome. A molecule that inhibits reverse transcriptase would prevent the DNA version from being made. Also full credit: A molecule that inhibits the integration of the DNA version of the viral genome into the host cell chromosome would prevent it from being copied. 3. The composition of the genetic material varies among viruses. Give two specific examples. Double-stranded DNA, single-stranded DNA, double-stranded RNA, single- stranded RNA. 4. Consider viruses. a) List the five phases of a viral life cycle. entry into the cell/insertion of viral genome replication of viral genome OR integration of viral genome into host cell chromosome production and assembly of viral proteins OR copying of viral genome with host cell chromosomes virions bud from host cell or lyse it/new generation leaves host cell/transmission to new host cell OR cell divides viral genome is transmitted to new host cell, new host, or new daughter cell b) Choose one of the five phases of the viral life cycle and describe how a drug could block viral replication at this stage. Indicate why this drug would not harm the host cell. Block entry or block genome replication or block processing/assembly of viral proteins. Drug must affect only viral genes or enzymes and not host cell genes or enzymes....
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