Test 5 - taches to the outside of the host cell (specific...

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ttaches to the outside of the host cell (specific interaction cannot stick to anything, host cell specific) epends on what kind of virus it is depends on how it gets inside hole virus goes inside – Euk nly nucleic acid – prok. Host machinery replicates viral genome and makes viral proteins (like capsid proteins) Of structural subunits and genome into capsid by budding or lysis of host cell; new virions can infect new host cell me ecules oli has no clue what is there, just extra piece of DNA, just part of the e coli genome, when cell divides so does viral genome, get out process Viral Replication o to a specific receptor on host cell, usually a membrane protein of either whole virus (eukaryotic) or just its genome (prokaryotic) o Viral nucleic acid inside the cell o Next step to make more viruses Virus must hijack host cells machinery The virus itself is not capable of making more viruses No RNA polymerase –transcription cannot be done by itself Makes for viral proteins and nucleic acid Typically many viruses being made inside o Break open host cell o Some leave by budding
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Host cell remains intact Also remains infected Basically leaves behind a little machine in the host cell that continues to send out viruses o Know 5 steps of virus life cycle o Do not get everything made at once, can take hours days or longer o Some enxymes needed to make viruses early on, then nucleic acid, then proteins Types of prokaryotic Virus Based on Life cycle o 1. Virulent virus (Ex. bacteriophage T4) Goes through five steps mean virulent and lyses Infects a cell and kills it (lytic cycle) Typically get multiple viruses attatching Bacteria viruses are called bacteriophages
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Seven genes in phage T4 – within ecoli cell, new T4 viruses being assemble, genetically all a little bit different, all have the seven Genes A-G, but have duplication of two others varying depending on where it was cut – have 9 genes total -- Seven – 5 single – 2 have double copies Bacteriophage Lambda (λ) o dsDNA temperate phage o infects E. coli Lytic or Lysogentic o Depends on concentration of 2 viral-encoded repressor proteins, Cro and CI o repressor proteins – bind to the operators of operons, block transcription of certain genes CI (lambda repressor) Represses genes involved in lysis o CI binds and prevents genes from send cell into the lytic pathway Required in low concentrations to maintain lysogeny Cro Represses genes involved in lysogeny
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o Prevents RNA polymerase from transcribing genes from lysogeny o Once commited to lytic pathway goes all the way through until next attachment step Needed in greater amount than CI to force λ into lytic cycle When lysogeny o Prophage can survive in a dormant host cell while virulent phages need active host cellular biosynthetic machinery o If the number of viruses > host cells, then a virus can continue to replicate as a prophage when its host cell divides.
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Test 5 - taches to the outside of the host cell (specific...

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