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Tobacco mosaic virus
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Foot and mouth disease virus
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Virology
1. Nature and Structure of Viruses
| Question | Answer |
|---|---|
| Tobacco mosaic virus | first virus to be recognized as filterable |
| Foot and mouth disease virus | first filterable animal virus |
| Yellow fever virus | first human virus |
| A. Negri | discovered inclusion bodies of rabies virus |
| P. Rous | first demonstration of a solid tumor virus |
| Rous sarcoma virus | solid tumor virus |
| Bacteriophages | discovered by Twort and d'Herelle |
| A. Woodruff and E. Goodpasture | reported on use of embryonated hen's egg as a host for viruses |
| J. Enders et al | reported that nonneural tissue supports poliovirus replication in culture |
| Knoll and Ruska | invented the electron microscope |
| Dmitri Iwanoski | Tobacco mosaic virus |
| F. Loeffler and P/ Frosch | Foot-and-mouth disease |
| Walter Reed et al. | yellow fever virus |
| Protozoa, fungi, and bacteria - unicellular or multicellular | unicellular |
| Protozoa, fungi, and bacteria possess the equipment for the production of ___ | metabolic energy and macromolecules |
| Example of macromolecules | nucleic acids, proteins, polysaccharides, and lipids |
| Viruses are dependen on ____ for functions | their cellular hosts |
| Virus particle is _____ outside a susceptible cell | metabolically inert |
| > 300 nm diameter (Bacterial, RC, Viruses) | Bacteria Rickettsia Chlamydophila |
| Obligate intracellular parasite (Bacterial, RC, Viruses) | RC Viruses |
| Plasma membrane (Bacterial, RC, Viruses) | Bacteria RC |
| Binary fission (Bacterial, RC, Viruses) | Bacteria RC |
| Possess both DNA and RNA (Bacterial, RC, Viruses) | Bacteria RC |
| Functional ribosomes (Bacterial, RC, Viruses) | Bacteria RC |
| ATP-generating metabolism (Bacterial, RC, Viruses) | Bacteria Maybe RC |
| Sensitive to antibiotics | Bacteria RC |
| Sensitive to interferon | Viruses |
| Viruses are _____ particles | submicroscopic particles |
| Viruses' genomes are elements of ____ | nucleic acid that replicate inside living cells |
| Viruses replicate by using ____ | the cellular synthetic machinery for the production of progeny virions |
| Virus | fluid poison or filterable viruses |
| Host range | range of animal species and tissue cells that the virus can infect |
| Host range for a given virus | broad or extremely limited |
| Structural unit | protomer protein subunit which may be assembled into capsomeres, may consist of one subunit or different protein subunits |
| Capsomeres | morphologicqal subunits from which the virus capsid is built |
| Capsid | protein shell or coat that encloses the nucleic acid genome |
| Envelope | a lipid-containing membrane that surrounds some viruses |
| Nucleocapsid | capsid together with the enclosed nucleic acid |
| Virion | complete infective virus particle |
| Viral attachment proteins (VAPs) | Capsid and envelope proteins that mediate the attachment of viruses to specific host cell receptors |
| Incomplete virion | virion without nucleic acid (empty capsid) |
| Defective virus | virus that cannot replicate b/c it lacks a full complement of viral genes |
| Replication only occurs | in mixed infections with a helper virus |
| Pseudotype | when related viruses infect the same cell, the genome of one virus may be enclosed in the heterologous capsid of the second virus |
| Pseudovirion | during viral replicaton, the capsid sometimes encloses host nucleic acid rather than viral nucleic acid |
| Pseudovirion - replicate? | look like ordinary viruses particles when observed by electron microscope, but do not replicate |
| Episome | autonomous extra-chromosomal genetic element |
| Provirus | viral DNA that is integrated into a host cell chromosome in a latent state and must be activated before it is transcribed |
| Provirus is transmissible from ____ | a parent cell to its daughter cell |
| Virus consists of ___, surrounded by a protein coat, ____ | nucleic acid capsid |
| Capsid - enveloped or nonenveloped? | could be either |
| Capsid are made up of ___ held together by ____ bonds | capsomeres noncovalent bonds |
| Most viruses have ___ capsid except for the ____ | one reoviruses |
| Reoviruses have ____ capsids | outer, middle, and inner |
| Cubic Symmetry | icosahedron pattern 12 corners/vertices/20 equilateral triangular faces, and 30 edges |
| Most efficient arrangement for subunits in a closed shell | cubic symmetry |
| Capsomeres are ___ in herpesviruses and reoviruses | hollow |
| Capsomeres are hollow in ____ | herpesviruses and reoviruses |
| Capsomeres located at the certices of icosahedral virions | Penton |
| Penton | Capsomeres located at the certices of icosahedral virions |
| Capsomes and nucleic acid molecules | self-assemble as a helix |
| Why is it not possible for "empty" helical particles to form | b/c of the interaction b/t capsid protein and nucleic acid |
| Incomplete virions | helical nucleocapsids |
| In all animal viruses, helical nucleocapsides are wound into ___ and ____ | into a coil and enclosed within a lipoprotein envelope |
| Complex viruses | some virus particles do not exhibit simple cubic or helical symmetry but are more complicated |
| Poxviruses | brick-shaped with ridges on the external surface and a core and lateral bodies inside |
| Capsid function | structural symmetry encases and protects facilitates attachment contain enzymes determines antigenic characters |
| Capsid encases and protects the viral nucleic acid from | nucleases in biologic fluids |
| Capsid facilitates the attachment of virus to | susceptible cells |
| Some capsids contain enzymes | which play roles in the infection process ex/ many viruses contain their own nucleic acid polymerases which transcribe the viral nucleic acid into mRNA |
| Capsids determine the antigenic characteristics of the virus | the host's protective immune response is directed against antigenic determinants of proteins or glycoproteins exposed on the surface of the virus particle |
| Enveloped virons acquired their envelopes when | the nucelocapsid buds from cellular membranes (cytoplasmic membrane, nuclear membrane, or Golgi complex) |
| Budding occurs only at sites where _____ have been inserted into the host cell membrane | virus-specific proteins |
| Envelope consists of | Virus-specified proteins Lipid bilayer |
| Virus-specified proteins associated with | receptor binding membrane fusion matrix protein |
| Receptor binding associated with | glycoprotein peplomeres, observed as spikes in electron micrographs |
| Membrane fusion associated with | fusion proteins |
| Polysaccharides are dervied from | the host cell |
| Fusion proteins are associated with | peplomeres and are involved in viral entry into and release from cells |
| Matrix protein found | a layer inside of some evelopes |
| Matrix protein serves as _____ for ____at plasma membrane | recognition site nucleocapsid |
| Matrix protein provides ____ to the envelope | added rigidity |
| Lipid bilayer derived from | host cell membrane |
| The integrity of the envelope is maintained ______, so it's readily disrupted by ____ | -maintained only in aqueous or moist environments -disrupted by drying, acidic conditions, etc |
| Solvents or detergents are used to ______ | disrupt the integrity of the envelope |
| Examples of solvents | ether chloroform |
| Examples of detergents | sodium deoxycholate |
| Disruptions of the envelope result in ______ except in some poxviruses | loss of infectivity |
| Capsids and envelopes both have ______ | viral attachment protein |
| Viral proteins | make up 50-70% of the virion |
| Examples of viral proteins | structural proteins regulatory proteins enzymes |
| Several viruses contain enzymes at are encoded in the _____ | viral genomes |
| Most important enzyme that is encoded in the viral genome | Polymerases |
| Polymerases | copies part of all of the genome of the virus, sometimes immediately upon entry into the host cell |
| Types of enzymes that are encoded in the viral genome | -enzymes transcribing the viral genome into mRNAs -enzymes involved in copying virion RNA and DNA -enzymes that copy the nucleic acid genome |
| Enzymes transcribing the viral genome into mRNAs | DNA-dependent RNA polymerase RNA-dependent RNA polymerase |
| DNA-dependent RNA polymerase ___ as template | DNA |
| RNA-dependent RNA polymerase ___ as template | RNA |
| DNA-dependent RNA polymerase: carried by DNA viruses such as ________ which replicate in the cytoplasm | asfivirus poxviruses |
| RNA-dependent RNA polymerase: carried by viruses with _____ | (-) sense RNA genome |
| RNA-dependent RNA polymerase: Host cells lack/have this enzyme | lack this enzyme |
| Enzymes involved in copying virion RNA into DNA | RNA dependent DNA polymerase |
| RNA dependent DNA polymerase | reverse transcriptase |
| RNA dependent DNA polymerase: Carried by ______ | hepadnaviruses retroviruses |
| Enzymes that copy the nucleic acid genome | DNA-dependent DNA polymerase RNA-dependent RNA polymerase |
| DNA-dependent DNA polymerase | copies the DNA genome |
| RNA-dependent RNA polymerase | replicase copies the RNA genomes |
| Viral nucleic acids | encode the genetic info necessary for replication of the virus |
| All viral genomes are haploid/diploid | haploid (they contain only one copy of each gene) |
| Genome may be ___________ | Monopartite or multipartite |
| Monopartite | all viral genes contained in a single chromosome |
| Multipartite | segmented ex/ viral genes distributed among several chromosomes that constitute the viral genome |
| DNA genome | genome of all DNA viruses of vertebrates is monopartite |
| DNA genome are double/single stranded | can be either double or single stranded |
| RNA genome | single stranded or double stranded monopartite or multipartite positive sense RNA genome negative sense RNA gemone |
| Positive-sense RNA genome | can function as mRNA in the infected cell |
| can function as mRNA in the infected cell | Naked RNA extracted from a (+) sense RNA virus is infectious when injected into host cell |
| Since mRNA can be directly translated into polypeptides, it is designated ____ | plus (+) mRNA |
| Viral nucleic acids | DNA genome RNA genome Viral lipids Viral glycoproteins |
| Negative -sense RNA | cannot function as mRNA, so virion carries own transcriptase enzymes |
| Injected naked RNA is infectious/not infectious | not infectious |
| Viral lipids | found only in the envelope |
| Viral lipids are a typical bilayer with ____ and in some cases, other viral proteins, embedded in it | virus-coded glycoprotein peplomeres |
| Viruses face harsh environmental conditions in the body and on the outside, including | pH changes bile salts proteases temperature osmotic changes sunlight dessication humidity |
| To maintain transmissibilty, and infection in a susceptible population, a virus must ___________ | overcome some of these conditions |
| Naked viruses survive well/ not well in the body and on the outside | survive well |
| _____ are more susceptible to environmental factors, such as gastric acidity, drying, and bile salts | Enveloped viruses |
| Viral surface proteins are denatured within a few mins at temperatures of _____, whicch make the viron incapable of normal cellular attachment, penetration, and/or uncoating | 55 to 60C |
| Acidic conditions can lead to _____ of the viral capsid | reversible or irreversible |
Created by:
DLS170