Exam 3 Pool Questions.docx - Question Pool 1(5 questions...

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Question Pool 1 (5 questions – you will be assigned one randomly on Exam 3) 1. Identify and explain each step of the virus replication cycle. 1. Attachment: virion binds to host cell using surface proteins that bind to specific structures. Highly specific. These interactions require tissue tropism. Most virus particles never encounter a host cell with the right chemical structure on it’s surface. 2. Penetration: viral nucleic acid gains access to site at which the nucleic acid will be expressed and replicated. Occurs by nucleic acid injection - Plant viruses penetrate via wounds or insect feeding and move from cell to cell through plasmodesmata, but move long distances throughout the plant through the bundle sheath - Uncoating in an animal host cell Latency: some viruses can enter a latent state, delaying replication until later 3. Macromolecule synthesis: viral nucleotide is replicated and the viral proteins including capsid proteins are made. Antiviral drugs interfere before and after this step. Expression of host genes is not required and competes with viral replication, transcription, and translation. Viral replication mechanisms can be complex and can vary widely. Requires host enzyme, specific viral genome encoded enzymes or a combo of both. Most virus DNA replication occurs in nucleus. Most RNA viruses replicate in the cytoplasm where eukaryotic host ribosomes make protein. 4. Assembly: capsid proteins and viral nucleic acid are assembled into nucleocapsids 5. Release: complete virions are released from infected cell, and if enveloped, the envelope is acquired at this stage 2. Compare and contrast the replication of a positive strand RNA virus and a negative strand RNA virus. RNA virus replication happens with a rolling circle mechanism and happens in the cytoplasm of a cell. Positive strand RNA acts as an mRNA template and produces it’s own replicase. Negative strand RNA on the other hand is more complex and bring the replicase protein with it when it enters the host cell.
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  • Spring '08
  • keen
  • DNA, host cell, viral nucleic acid, virus replication cycle, strand RNA virus

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