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33 Cards in this Set
- Front
- Back
24.1
viruses |
- obligate intracellular parasites
- genome contains either RNA or DNA as the genetic information. - protective protein shell (capsid) surrounds the nucleic acid genome and frequently the capsid is enclosed within an envelope (contains both protein and lipid) |
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24.2
viral assembly |
- occurs by the process of self-assembly by which the component parts aggregate into the proper configuration
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24.3
bacteria vs. viruses size and visability |
size:
bacteria: > 500 nm viruses: < 300 nm visability: bacteria: light microscope viruses: electron microscope |
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24.4
bacteria vs. viruses filterability and cultivation |
filterability:
bacteria: non-filterable (remian on top of the filter) virsus: filterable (pass through) cultivation: bacteria: artificial media viruses: living host cells |
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24.5
bacteria vs. viruses replication and nucleic acids |
replication:
bacteria: binary fission viruses: complex nucleic acids: bacteria: DNA + RNA viruses: DNA or RNA |
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24.6
viral morphology |
- 20-25 nm (parvoviruses and picornaviruses)
- 200-300 nm (poxviruses) - symmetry of protein coat or capsid surrounding the nucleic acid can be either helical or cubical (icosahedral) both together are referred to as nucleocapsid - capsid is composed of subunits or capsomers - capsomers: used to build more complex icosahedral capsids - single polypeptide chains are used to build the helical capsids |
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24.7
icosahedral symmetry |
- cubic symmetry found in viruses is based on the icosahedron which has 20 faces, each an equilateral triangle, 12 vertices and 30 edges
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24.8
helical symmetry |
- capsomers and nucleic acid genomes of several RNA viruses undergo self-assembly as a cylindrical nucleocapsid in which the capsomeres are arranged like a spiral staircase or helix
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24.9
complex |
- virus doesn't fall into either of the groups above (poxvirus)
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24.10
naked icosahedral |
- these viruses consist of icosahedral nucleocapsid (parvoviruses, picornaviruses, adenoviruses)
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24.11
envloped icosahedral |
- the virion of this group consists of an icosahedral nucleocapsid surrounded by an envelop (herpesviruses, togaviruses)
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24.12
naked helical |
- these viruses appear to be long rods; however they consist of an RNA genome interwined with protein structural units to form a helix. Although none of the animal viruses are in this group, many of th eplant viruses are (tobacco mosaic virus)
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24.13
enveloped helical |
- viruses in this group consist of a flexible helical nucleocapsid surrounded by an envelope.
- orthomyxoviruses and paramyxociruses |
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24.14
complex ciruses |
- some viruses do not fit into any of the above categories. The poxviruses are the most complex of the animal viruses
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24.15
viral nucleic acid |
- either DNA or RNA, generally not both
- all viral genomes are haploid and contain one copy of each gene, except retroviruses which are diploid |
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24.16
DNA viruses: nucleic acid |
- may be single or double stranded including both linear and covalently closed circular DNA
- largest DNA viruses - poxviruses and herpesviruses - 100-200x10^6 daltons. - 2 strands of poxvirus DNA are covalently cross-linked at their termini, so that on denaturation the molecule becomes a large single-stranded circle |
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24.17
RNA viruses: nucleic acid |
- genome may be single or double stranded either segmented or nonsegmented.
- arenavirus genomes have 2 segments, bunyavirus genomes have 3 segments, orthomyxovirus has 7 or 8, and reovirus has 10, 11 or 12 segments |
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24.18
RNA viruses are classified according to: |
whether the RNA is of the same polarity as mRNA (+ strand_ or whether RNA is of th eopposite polarity to mRNA (- strand)
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24.19
picorna and togaviruses |
some RNA viruses like Picorna and Togaviruses contain RNA which exists as a non-segmented RNA. At the 3' end is a polyadenylic acid chain similar to eurkaryotic mRNA
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24.20
the flu |
- influenza A virus contains 8 segments of RNA
- surrounding the gentic material is a capsid containing the following peplomers (glycoproteins) - hemagglutinin (HA) assists the virus awith attaching to the host ell - neuraminidase is responsible for the release and spread of the virus |
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24.21
antigenic drift |
- occurrence of point mutations whithin HA and neuraminidase.
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24.22
antigenic shift |
- 2 different strains of a virus, combine to form a new virus, having a mixture of the different surface antigens of the 2 original strains
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24.23
terminal redundancy |
- nucleic acid of several viruses are terminally redundant or repetitious. Their base composition may be respresented as ABC...XYZA
- herpesvirus DNA: length of the repeated sequence is about 400 nucleotide base pairs. Terminal redundancy of this type is also exhibited by the RNA or RNA tumor viruses - other virus genomes like adenovirus, parvovirus, and poxvirus DNAs are also terminally redundant but here the reported sequences are inverted or reversed |
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24.24
segmentation |
- genomes of various RNA viruses including reoviruses (10 segments), rotaviruses (11 segments), influenza viruses (8 segments) have been shown to be segmented
- genome of RNA tumor viruses: 2 identical single-stranded RNA molecules -> diploid genome |
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24.25
genetic relatedness of viral nucleic acids |
- determination of similarity is measured by how extensively their nucleic acids can hybridize. this is done by denaturing dsDNA to single-stranded state and allowing the strands to reanneal. If the genomes are related, pairing will occur, if not then no pairing (hybridization) will occur.
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24.26
infectivity of animal virus nucleic acids |
- viral nucleic acid contains all the info for the virus particle. The nucleic acid of picornaviruses, togaviruses, coronaviruses, papovaviruses, adenoviruses and herpesviruses are infectious.
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24.27
glycoproteins |
- viral envelopes contain glycoproteins (hemagglutinins) in the form of spikes or projections.
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24.28
hemagglutination |
- both enveloped or naked biruses can agglutinate RBCs of certain animal species. RBCs contain receptors on their surface for hemagglutinins on the virus particle.
- hemagglutination titer can be used to quantitate total virus numbers |
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24.29
viral envelopes contain: |
- complex mixtures of neutral lipids, phospholipids and glycolipids.
- composition usually reflects that of the membranes of the host cell from which envelope virus bud. \- therefore viruses grown in different tissue culture cells may contain envelops with widely different lipid compositions. |
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24.30
vesicular stomatitis virus |
- single stranded RNA virus and looks bullet shaped, just like rabies. both of these viruses are easy to lyse with detergents
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24.31
adenovirus |
- has no envelope and has a capsid with a hexon/penton structure
- uses its tail fibers to attach to epithelial cells |
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24.32
papillomavirus |
- looks similar to adenovirus
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24.33
vaccinia virus |
- a pox virus with complex morphology
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