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47 Cards in this Set
- Front
- Back
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____ is a genetic element that cannot replicate independently of a living (host) cell.
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virus
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virus particle
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extracellular form of a virus; allows virus to exist outside host and facilitates transmission from one host cell to another
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____ is the infectious virus particle; the nucleic acid genome surrounded by a protein coat and, in some cases, other layers of material
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Virion
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Viruses only infect certain type of life forms. t/f
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f. can infect all types of life forms
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what are the most important roles of viruses?
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limit population density of host (without their extinction_
select for host diversity (by preventing dominance of any one species) |
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Viruses are obligatory intracellular parasites that DNA or RNA with a large genome. t/f
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f. their genomes are very small (b/w 3 - 50kb)
means that it needs components from host. |
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Viruses contain have spikes. t/f
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t
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viruses can infect all types of cells in one host. t/f
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f. most viruses infect only specific types of cells in one host
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what is a viruses host rage determined by?
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by specific host attachment sites and cellular factors
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___ the protein shell that surrounds the genome of a virus particle
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capsid
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what is the smallest morphological unit visible with an electron microscope?
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capsomere
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nucleocapsid
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complete complex of nucleic acid and protein packaged in a virion
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in capsids with ____ ____ , the subunits pack about the roational axes to form closed structures.
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rotational symmetry
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capsids with ___ ___ tend to form more open-ended structures, with subunits added in a spiraling array
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helical symmetry
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an example of rotational symmetry
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icosahedral symmetry
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a virus that has helical symmetry
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ebola
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envelopes make the initial contact with host cells. t/f
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t
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what are the components of a virus?
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capsid
dna sheath tail fiber pin baseplate |
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what are the enzymes critical to virion infection ?
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lysozyme
nucleic acid polymerases (reverse transcriptase) or RNA pol neuramidases |
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what are neuramidases?
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enzymes that cleave glycosidic bonds in glycoproteins and glycolipids, and allow liberation of viruses from host.
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___ is the number of infectious units per volume of fluid
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titer
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what is one of the most accurate ways to measure virus infectivity?
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plaque assay
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assaying foci
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animal viruses that do not kill their host cells can be detected using that method
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serological tests
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use antibodies to identify virus antigens.
detection of antibodies aganist viruses in a patient. |
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nucleic acid-base tests
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restriction fragment length polymorphism (RFLP) or PCR of isolated viral genomes or genome fragments
nucleic acid hybridization |
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lytic cycle
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phage causes lysis and death of host cell.
generalized transduction |
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what is generalized transduction?
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DNA derived from any portion of the host genome is packaged inside the mature virion in plave of the vitus genome.
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lysogenic cycle
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virus DNA is incorporated into the host DNA (prophage)
Phage conversion specialized trasduction |
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_____ ____ when lysogenized by a phage, the host cell becomes immune to further infection by the same type of phage.
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phage conversion
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specialized transduction?
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DNA from a specific region of the host chromosome is integrated directly into the virus genome, usually replacing some viral genes.
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what are the five steps of the lytic cycle?
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attachment
penetration biosyntesis maturation release |
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what happens during the eclipse period in a one-step viral growth curve?
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synthesis of nucleic acids and protein coats.
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what are the six steps for replication in animal viruses?
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attachment
penetration uncoating biosynthesis maturation release |
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Production of ____ occurs first when viruses infect a host?
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mRNA
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_____ transform normal cells into cancerous cells
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activated oncogenes
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virus-transformed cells contain ____ and exhibit____
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contain virus-specific cell surface antigens.
exhibit increased growth, loss of contact inhibition, and certain chrosomosomal abnormalities, such as unusial numbers of chromosomes and fragmented chromosomes. |
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what are the 5 examples of oncogenic DNA viruses?
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adenoviridae
herpesviridae poxviridae papovaviridae hepadnaviridae |
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what are examples of oncogenic RNA viruses?
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viral RNA is transcribed into DNA which can integrate into host DNA
Retroviridae |
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____ results when virus replication kills the target cells.
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lytic infections
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virus infection may induce apoptosis. t/f
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t
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what are syncytia
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cell surface expression of viral glycoproteins triggers the fusion of neighboting cells into multinucleated cells
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what is the advantage of syncytia formation?
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allows viruses to spread from cell to cell and to escape antibody detection.
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latent infections
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viruses remain in asymptomatic host cells for long period of time until reactivation. ex: cold sores or shingles
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Persistent infection
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disease processes occur gradually over a long period of time and are often fatal. measles virus
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what is the classification system of viruses based on?
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genome composition
symmetry of the capsid envelope size host range |
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viral species
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a group of viruses sharing the same genetic information and ecological niche
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what are the seven groups viruses are divided into?
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g1: dsDNA
g2: ssDNA g3: dsRNA g4: +ssRNA g5: -ssRNA g6: RNA retroviruses g7: DNA pararetroviruses |
