Term
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Definition
Obligate inracellular parasites
Require host cells to reproduce
10-100 nm |
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Term
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Definition
| Yellow fever (human disease) was caused by a virus transmitted by mosquitos |
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Term
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Definition
| Virus that only attacks bacteria |
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Term
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Definition
| Reverse mechanism to change RNA to DNA to put it into your cells |
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Term
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Definition
Single or double or partially stranded DNA or RNA
Capsid and sometimes envelope |
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Term
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Definition
Protein shell composed of many capsomere proteins
Surrounds the genome
Helical or icosahedral symmetry |
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Term
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Definition
| Capsid and the genome together |
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Term
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Definition
Plasma membrane around the capsid
Virus is "naked" if it doesn't have one |
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Term
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Definition
| Adhere, penetrate, uncoat, early synthesis, late synthesis, assembly, and exit. |
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Term
| Most important part in the viral replication cycle |
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Definition
| Entry: in animal cells, they don't have to contend with a cell wall. In other cells, they do. |
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Term
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Definition
| Many are enveloped. Not all infections end in cell lysis or cell death. |
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Term
| Why are animal viruses enveloped? |
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Definition
| The envelope allws it to get into the host cytoplasmic membrane. |
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Term
| What results do some animal viruses have on cells? (not including lysis) |
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Definition
| Persistent infections, latent infections, and transformation. |
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Term
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Definition
| Release of viruses from host cell does not result in cell lysis. The cell remains alive and produces viruses indefinitely. |
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Term
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Definition
| Delay between infection by the virus and lytic events. |
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Term
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Definition
| Conversion of a normal cell into a tumor cell. |
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Term
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Definition
| Entry often depends on some damage already mead to the plant tissue in order to open a spot in the cell wall. |
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Term
| How can we grow and quantify viruses? |
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Definition
| They are small (can't use a compound microscope) and only replicate in host cells, so strategies are used to amplify and quantify the viruses. |
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Term
| Two types of bacteriophages |
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Definition
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Term
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Definition
| Phage will replicate in and burst open (lyse) host |
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Term
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Definition
| Phage can integrate its genome into the host cell (becoming a prophage), and it can be replicated each time the host cell replicates. |
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Term
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Definition
| Where the cells still are |
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Term
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Definition
| Indicates cell death / lysis. One virus leads to one plaque, similar to one cell leads to one colony. |
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Term
| Cultivating animal viruses |
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Definition
| Viruses are grown in tissue cultures (usually Hela cells), which must be kept sterile and bacteria-free. CPE can be observed in infected cultured cells. |
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Term
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Definition
1. Simple filtration will remove large cells and cellular debris.
2. Differential centrifugation AND gradient centrifugation |
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Term
| Viral purification: Gradient centrifugation |
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Definition
| Depends on density. Each piece of different density will settle into a different area (or band) of the density gradient after centrifugation. |
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Term
| Virus quantification: direct count |
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Definition
| Electron microscope can be used to visualize a known volume of material, counting the viruses in it and scaling it up to determine the titer. |
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Term
| Problems with direct count |
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Definition
Expensive, specialized microscope required.
Can't differentiate between infectious and noninfectious viral particles. |
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Term
| Virus quantification: hemagluttination assay |
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Definition
| Exploits the trait of some viruses to stick to red blood cells, causing themto form a gel mat. |
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Term
| Benefits of the hemagluttination assay |
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Definition
| Cheap, easy, fast. No microscope needed. |
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Term
| Problems with the hemagluttination assay |
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Definition
| Some viruses won't work, and it doesn't give an exact number. The assay also doesn't differentiate viable vs. nonviable viruses. |
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Term
| Virus quantitation: endpoint assays |
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Definition
TCID50 - the amount of virus needed to induce CPE in 50% of culture cells.
LD50 - amount of virus needed to kill 50%of test animal subjects |
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Term
| Types of virus quantitation |
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Definition
| Direct count, hemagluttination assay, endpoint assay |
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Term
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Definition
| Tissue culture infectious dose 50 |
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Term
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Definition
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Term
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Definition
| Simple letter / number combination; organism they infect; location of discovery; appearance; disease caused |
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Term
| Virus classification: ICTV classification scheme |
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Definition
| Classify based on order,family, subfamily, genus, and species. |
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Term
| Virus classification: The Baltimore classification system |
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Definition
| Developed by David Baltimore. Based around mRNA production methods. Separates viruses into 7 classes. |
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