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32 Cards in this Set
- Front
- Back
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What are 5 characteristics of viruses?
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1. Can'tsee w/ lite microscope
2. Have to use EM 3. Obligately intracellular 4. Have RNA/DNA, not both 5. Don't respond to antibiots |
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What is the smallest/largest virus?
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Smallest = Polio
Largest = Pox |
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What are 4 characteristics of viral structure?
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1. Nucleocapsid
2. Virion vs. viroid 3. Naked vs. Enveloped 4. Symmetry |
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What is the nucleocapsid?
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the nucleic acid and capsid
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What is a virion?
What is a viroid? |
Virion = virus w/ complete capsid and nucleic acid.
Viroid = incomplete, doesn't have a capsid. |
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What is an Envelope?
How does it form? |
extra outer layer - a capsule.
-Formed by picking up some membrane during budding of virus from host cell. |
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What are the 2 types of symmetry?
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1. Icosahedral (cubic)
2. Helical (coiled) |
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What are the 6 steps in Viral replication?
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1. Adsorption
2. Penetration 3. Uncoating (eclipsing) 4. Nucleic acid replic/protein coat synthesis. 5. Assembly 6. Release |
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What occurs in adsorption?
Penetration? |
Ads: viruses binds to host cells w/ the receptor for it.
Pen: by phagocytosis or melding |
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What occurs in Uncoating?
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Eclipsing - the cell's enzymes release the nucleic acid from the capsule.
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What occurs in the course of viral nucl. acid replication and protein synthesis?
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the viral nucleic acid is replicated using the host's machinery, and new capsomeres are synthesized (protein) to make the capsid.
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What is interesting about the assembly process of viruses?
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It is the least efficient step in the whole replication process.
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What happens if viral assembly is incomplete?
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Pieces get left in the host cell and can be seen on a tissue biopsy as INCLUSION BODIES.
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Where does a DNA or RNA virus assemble?
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DNA = in the host's nucleus
RNA = in the host's cytoplasm. |
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How is the virus released after assembly and all?
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It depends on the type of virus - whether enveloped or not.
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How does each release:
-Enveloped -Naked |
-Env released by budding
-Naked released by lysis. |
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What are the 5 steps in viral infection of host cells?
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1. Transmission
2. Port of entry 3. Binding to specific receptor 4. Active infection 5. Latent infection |
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What type of viruses especially cause latent infections?
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DNA viruses - like the herpes virus w/ cold sores.
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what is a latent viral infection in bacteria called?
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Lysogeny
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How does lysogeny affect C. diphtheriae?
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The virus encodes the exotoxin produced by the bacteria, and is released upon lysis.
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What are 3 host defenses to viruses?
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1. Humoral
2. Cellular 3. Interferon |
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How does each defense work -Humoral
-Cellular -Interferon? |
Humoral Prevents infection
Cellular helps recover Interferon is species spcf and prevents a runaway infection. |
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How does interferon prevent spread of infection?
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It is released from infected cells and protects neighbors.
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What are 7 methods for identifying viruses?
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1. Tissue cultures (CPE)
2. Shell vial assays 3. Animal/chick embryo inoculat. 4. Cytological exam of host tissue 5. Immunological tests 6. Serological tests 7. molecular methods |
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What is CPE?
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Cytopathic effect
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What are 6 effects viruses can have on host cells?
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1. None
2. Inclusion bodies 3. Giant cells 4. Cell death 5. Proliferation 6. Chromosomal changes |
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What does the location of an inclusion body tell about the virus?
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-If in nucleus of cells, its a DNA virus
-If in cytoplasm, an RNA virus. |
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How do viruses cause giant cells?
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by causing nuclear divisions without cytoplasmic.
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What's an example of prolif caused by a virus?
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warts
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How do you do a tissue culture?
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-Put down a monolayer of cells.
-If tube, use roller drum to keep virus on all cells. -Look for CPE |
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What is a shell vial assay, how is it done?
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1. monolayer of cells on coverslip
2. add specimen; centrifuge at 35 for 30-45 minutes 3. Incubate for 24 hrs 4. Flood with Ab-flour 5. Incubate, wash, UV scope |
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What information is being sought when identifying viruses?
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-Time takes for growth
-Cytopathic effect it has -Type of cell line it grows on |
