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192 Cards in this Set
- Front
- Back
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Tobacco mosaic virus
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First virus to be recognized as filterable
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Foot-and-mouth disease virus
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First filterable animal virus
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Yellow fever virus
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First human virus demonstrated by Walter Reed
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A. Negri
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Discovered the inclusion bodies of the rabies virus
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Bacteriophages
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Viruses that multiply exclusively in bacteria, and do not cause disease in animals
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These 2 men reported on the ues of the embyonated hen's egg as a host for viruses
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A Woodruff and E Goodpasture
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J Enders
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Discovered that non-neural tissue will suppoort polio virus replication in culture.
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Knoll and Ruska
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Invented the electron microscope
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T or F a virus is a cell
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False. A virus is not a cell. Outside a suseptible cell, the virus is metabolically inert.
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T or F a virus has both DNA and RNA
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False. A virus will only have one or the other.
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The structural unit of a capsomere
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Protomer
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The structural unit of a capsid
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Capsomere
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The protein box or shell that encloses the nucleic acid genome
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Capsid
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Envelope
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A lipid containing membrane that covers SOME viruses
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Nucleocapsid
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The capsid together with the enclosed genetic material
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Virion
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Virus
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Incomplete virion
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Empty capsid with no genetic material.
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Defective virion
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A virus that can not replicate because it lacks a full set of genetic material.
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T or F a defective virion can replicate
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True, only in the presence of a helper virus though. If no helper is present then it is unable to reproduce
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Pseudotype
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If 2 different viruses are in the same cell during replication, they can exchange protein coats. They "look like" the other virus.
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Pseudovirion
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During replication, the hosts DNA became encapsulated in the capsid. They "look" like normal viruses, but do not replicate
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Episome
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Extra-chromosomal genetic material. Analgous to plasmid in BacT.
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Provirus
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Viral DNA that is integrated into host DNA. This is a permanant change.
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What family of virus has more then 1 capsid?
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Reoviridae have 3 capsids. An outer, middle and inner capsids.
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Icosahedron
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Cubic symmetry. Solid with 12 corners, 20 equilateral triangluar faces, and 30 edges.
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Helical symmetry
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These capsomeres self assemble in a helical fashion. They are NEVER incomplete.
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T or F Helical viruses can be naked or enveloped
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False. They are always enveloped
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Functions of a capsid
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Structural symmetry of of the virus particle, Encases the nucleic material, facilitates attachments.
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2 chemicals that dissociate viral envelopes
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Chloroform, detergents (such as sodium deoxycholate)
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Enzymes transcribing the viral genome into mRNA's
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DNA-dependant RNA polymerase (replicates in cytoplasm)
RNA-dependant RNA polymerase (carried by neg sense RNA viruses) |
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RNA-dependant RNA polymerase
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Neg sense RNA viral genomes carry this. A host cell does not carry this enzyme.
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Enzymes associated with copying virion RNA into DNA
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RNA-dependant DNA polymerase. Reverse transcriptase
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Reverse transcriptase
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AKA RNA-dependant DNA polymerase. Found in Hepadnaviruses, and retroviruses
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Enzymes that copy the nucleic acid genome
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DNA-dependant DNA polymerase
RNA-dependant RNA polymerase |
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Replicase
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AKA RNA-dependant RNA polymerase. Copies the RNA genome
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Diploid viral genome
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Retrovirus genomes
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Haploid viral genomes
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All viral families except retroviruses
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The DNA genome of all vertebrates
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Monopartite
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Positive sense RNA genome
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Can serve as mRNA and is immediatly infective when injected into a cell
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Negative sense RNA genome
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Cannot function as mRNA, and is not immediatly infective when injected into a cell.
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Viral lipids
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Only found in envelope
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Viral glycoproteins
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Membrane bound spike, which extend from the envelope
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stability of naked vs enveloped viruses
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Naked viruses are generally more stable
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2 single stranded DNA viruses
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Circoviridae, Parvoviridae
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The only DNA virus that is not icosahedral
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Poxviridae (complex)
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Parvoviridae
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Very small virus. Replication only occurs in actively diving cells (in nucleus) acidophilic intranuclear inclusion bodies. Very resistant
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Papillomaviridae
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Very small. Produce chronic infection. May be episomal or proviral. Replicates in nucleus. Resistant
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DNA viruses that have an envelope
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Herpesviridae, Asfarviridae, Iridoviridae, Poxviridae
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Naked DNA viruses
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Circoviridae, Parvoviridae, Hepadnaviridae, Papillomaviridae, Polyomaviridae, Adenoviridae
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Adenoviridae
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Medium sized. Posseses filaments/fibers which project from the vertex capsomeres. Replicates in nucleus. Basophilic intranuclear inclusion bodies. Narrow host range, and will cause latent infections that resurface with immunosupression.
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Asfar
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African Swine Fever And Related (viruses)
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Asfarviridae
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Large virions, that replicate in the cytoplasm (though the nucleus is needed for DNA synthesis) Only one pathogen (Asfivrus)
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Herpesviridae
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Replicates in nucleus. Produces acidophilic intranuclear inclusion bodies. Very fragile and requires close contact for transmission. Can induce cytomegaly, syncytia or are oncogenic. Lifelong persistant infection.
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Poxviridae
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Largest virion. Complex structure. Replication entirely in cytoplasm. Can be enveloped or non enveloped. Eosiniphilic intracytoplasmic inclusion bodies. All pox viruses cause scabs. Can survive for many years in dried scabs.
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Hepadnaviridae
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Partially double stranded, and partially single stranded DNA. Replicate in nucleus of hepatocytes. Reverse transcriptase! Acute and chronic hepatitis
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Circoviridae
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Smallest known viruses. Single strand DNA. Replication occurs in nucleus of cells in "s" phase of cell cycle. Produces large intranuclear/intracytoplasmic inclusion bodies
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Polyomaviridae
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Small viruses. Innapparent infections. Highly host specific. Replicates in host cell nucleus.
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Double stranded RNA viruses
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Reoviridae, Birnaviridae
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Multipartite RNA viruses
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Reoviridae, Birnaviridae, Bunyaviridae, Arenaviridae, Orthomyxoviridae
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Picornaviridae
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Small, ether resistant. SS positive sense. Replication in teh cytoplasm. Rapidly cytolic so infection is generally acute. many serotypes, with little cross protection
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Caliciviridae
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Small, with cup shaped depressions on surface of capsid. Positive sense. Replication in cytoplasm.
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Togaviridae
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Positive sense. Has envelope on an icosehedral nucleocapsid. Replication in cytoplasm. Infection is acute and cytolytic. EEE
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Arteriviridae
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Positive sense with envelope. Replication in cytoplasm. Primary host is macrophages, and persistant infections are common.
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Flaviviridae
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Positive sense with envelope. Replication in cyoplasm, and assembly involved envelopment in endoplasmic reticulum. cytolytic
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REO-viridae
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Respiratory Enteric Orphan
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Reoviridae
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Medium sized, with 2 to 3 capsids. Genetic reassortment in dual infections. Replication in cytoplasm. Acidiophilic intracytoplasmic perinuclear inclusion bodies.
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BIRNA-viridae
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Bi-RNA (2 segments of RNA)
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Birnaviridae
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Medium sized with 2 molecules of double stranded RNA. Assembly in cytoplasm.
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Coronaviridae
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Envelop has club shaped surface peplomers arranged in a fringe like a crown. Positive sense. Replication in cytoplasm, and will bud through the endoplasmic reticulum and golgi membranes. Narrow host range with persistant infections.
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Naked RNA Viruses
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Reo, Birna, Picorna, Astro, and Calici
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Primary cell cultures are used for what?
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Producing viral vaccines
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Serially propagated cell cultures
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Homogenous population of a single cell type derived from human embryos or subcultres of a primary culture.
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How many times can a serially propagated cell culture be sub-cultured?
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Up to 100 times before growth stops
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Continous cell lines are also known as what?
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Heteroploid cell lines
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What are continous cell lines?
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These are cells of a single type that are capable of indefinite propagation in vitro.
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Where are continous cell lines derived from?
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Cancerous cells, or by treating primary cell cultures or diploid lines with a mutagenic chemical
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What is the first step in creating a primary cell culture
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Organ/Tissue is minced and treated with a protease
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After cells in a primary culture are treated with proteases, what happens
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The cells are washed coutned and diluted in a growth medium and allowed to settle on the flat surface of a glass or polysterene container
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Shell vial (1-Dram) cell culture
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A coverslip with a monolayer is inside of glass vial. used in centrifuged enhanced innoculation
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Co-Cultivated cells
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This involves the combination of different cell types grown together as a single monolayer
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At what age are embryonated eggs used for culture?
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5 to 13 days
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Yolk sac innoculation is used for what viruses?
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Togaviruses and avian enterovirus
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Chroioallantoic membrane (CAM) is used for what viruses?
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Poxvirus and some herpesvirus
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Amniotic route is used for what virus?
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Influenza A viruses
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Allantoic route is used for what kind of viruses?
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Influenza A, Newcastle, infectious bronchitis virus
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Intravenous egg innoculation is used for what virus?
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Ovine Orbivirus (bluetongue)
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Rabbits are commonly used for production of what?
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Antisera
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Mice are commonly used for what?
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Implantation of intraperitoneal hybridomas
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A quantitative determination of viral activity
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A virus titration
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Virus titer
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The number of infectious units per mL of sample
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Quantitative Assay
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Measures the exact number of infectious particles in the sample. The monolayer plaque assay is the most common
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Virus quantitation
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How infectious a virus is
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Monolayer plaque assay
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A single sheet of cells. Plaque forms from necrotic colorless cells, while being surrounded by viable cells that are stained with a vital dye. The reason this is used is bc you can see what cells were infected by the virus. (hence it is a virus quantitation)
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PFU
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Plaque forming units (is the unit used in quantitation assays)
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titer is measured in what units?
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PFU/mL
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CAM
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Pock assay - infection of chorioallantoic membrane
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TCID50
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Tissue Culture Infectivity Dose 50
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Quantal Assay
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Determines presence or absence of an infection (does not measure the exact amount of particles)
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Permissive cell
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a cell that has all the needed parts for virus replication (this leads to a productive infection)
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What kind of cell leads to a productive infection
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Permissive cell
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Nonpermissive cell
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A cell that does not allow for full virus replication. (these can become cancerous)
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An abortive or non-productive cells is known as what?
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non-permissive cell
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MOI (Multiplicity of infection)
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the number of infectious viruses inoculated per cell. (usually 5-10 PFU per cell)
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Eclipse period
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time from viral uncoating to when progeny is detected intracellulary
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With enveloped viruses, when does the eclipse period end?
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It occurs when they are realsed extra cellularly (because prior to that, they have no antigenic proteins)
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Latent period
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During this period viruses can not be detected
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In general, DNA transcription and replication occurs where?
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Inside the cell nucleus (not in pox, irido, and asfar)
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T or F An enveloped virus that suses surface fusion will cause an infected cell to undergo ADCC?
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True - Post fusion, the cell then has a new antigenic specificity and becomes a target for ADCC and complement mediated cytolysis.
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transcirption
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Process where nucleic material is transferred to mRNA
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What is the function of capping?
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Capping stabilizes mRNA and aids in aligning the mRNA with the ribosomes
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where does the Poly A attach
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At the 3' end of RNA
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Splicing of viral pre-mRNA
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you delete introns (non coding)and ligate exons (coding) via spliceosomes
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what is the function of spliceosomes?
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To delete introns and ligate exons
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mononcistrionic mRNA
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Codes for one gene in a genotype
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Polycistrionic mRNA
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Codes for multiple genes in a gentoype
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How does a DNA virus replicate?
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via DNA-dependant RNA polymerase
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how are negative sense RNA viruses transcribed?
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via RNA-Dependant RNA Polymerase
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Translastion
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Processed viral mRNA bind to ribosomes and are translated into proteins.
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Helicase
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promotes unwinding of the DNA double helix
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Double stranded DNA goes through what kind of replication?
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Semi conservative replication
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Extracellular spread (type 1 spread)
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Virions are released from the cell to spread in the ECF
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Intercellular spread (type 2 spread)
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Virions spread cell to cell via desmosomes without having to enter the ECF. these usually result in long term infections.
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Nuclear spread (type 3 spread)
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The viral genome is latent, and becomes incorperated into host genes. It is then passed from parent to progeny during cell division.
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how are the viral effects on cells classified?
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Cytocidal (cytolytic, cytopathic) noncytocidal (nonlytic), and cell transformation
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What is CPE? (cytopathic effect)
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It is the visible or morphological changes induced in a host cell by a virus. These changes can cause damage or death.
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Inclusion bodies of herpesvirus
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"owls eyes" intranuclear acidophilic with syncytium
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What creates intracytoplasmic, perinuclear acidophilic inclusion bodies?
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Reovirus
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Name 3 types of cytocidal changes seen in affected cells
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-inhibition of host cell DNA replication
-inhibition of host cell RNA transcription -Inhibitionof processing of host cell mRNA's |
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Define cell transformation
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it is the changing of a normal cell in to a cancer cell.
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Proto-oncogenes
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Control normal cell growth
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Cellular oncogenes
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Abnormally expressed or mutated corresponding proto oncogenes that are involved in the process of producing non-viral tumors
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Tumor suppressor genes
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Act to inhibit cell proliferation by holding the cell cycle at G1. Also known as a negative regulator
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Rb protein
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Will stop a cell from dividing by keeping it at S phase
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p53 protein
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Acts for cell cycle arrest at S1 phase, as well as inducing apoptosis
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Which DNA families can cause tumors?
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PPP, HH, A
Papilloma, polyoma, pox Herpes, Hepadna Adeno |
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How do DNA viral tumors grow?
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By supressing the tumor suppressor genes (p53, Rb)
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All RNA tumor viruses belong to what family?
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Retroviridae
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Are RNA viral tumors deterimental to the host cell
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No, therefore they are oncogenic and productive cells.
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Acute transforming viruses
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V-Onc+ these are derived from the host cell proto oncogenes
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Chronic transforming retroviruses
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V-Onc- the viruses lack V-Onc genes and are weakly oncogenic. there must be a mutation that results in enhanced expression of proto oncogenes
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Escape mutants
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These are mutations effecting antigenic determinants. these result in persistant infections
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Conditional-lethal mutants
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A virus that can not grow under certain conditions (as in a nonpermissive cell) but can grow in a permissive cell
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Temperature sensitive mutants (Ts)
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Used in creating vaccines. these grow as low (permissive) temperatures and not at high (nonpermissive) temps
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Defective Interfering (DI) mutants
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it lacks one or more functional genes required for viral replication due to a deletion mutation.
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Dual infection
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If 2 viruses are dissimilar enough they can both replicate in the same cell with no problem.
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Genetic interactions
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Interactions between different genomes. Progeny are geneticlly different then either parent.
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Genetic reassortment
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Happens in multipartite viruses only.
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Genetic recombination
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"crossing over" Can happen with host genetic material also.
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Viral interference
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A superinfecting virus becomes inhibited by introduction of a less virulent strain into the population
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Pathogenicity
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the abilty of an organism to cause disease by overcoming the defenses of the host
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What are the most important portals of entry
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respiratory tract, GIT, and skin
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What is the most common portal of entry
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Repiratory tract
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Virulence
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The capacity of an organism to cause disease in comparison to another closely related virus
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Suseptible cells
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Cells that become infected but do not contribute to a disease
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Target cells
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Cells that become infected who's infection will contribute to clinical signs
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Signs
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Objective
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Sympotoms
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Subjective
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Viremia
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The presence of blood in the blood stream
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Passive viremia
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Direct innoculation of the bloodstream (ie arthropod vector, iatrogenic infection)
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Primary viremia
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The release of progeny virus from the site of inital viral replication (which is the portal of entry into the bloodstream)
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Secondary viremia
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Release of progeny from the secondary site of infection (usually the bloodstream) and will ALWAYS cause disease
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Nuetralizing antibodies will act on what type of viruses?
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Free in the plasma viruses (ie toga, parvo, flavivi)
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Where do neural spread viruses move?
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These are transported withing axons, endoneural space, perineural lymphatics, or in infected schwann cells. Some can use olfactory nerve endings
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Centripetal movement
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Towards the CNS
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Centrifugal movement
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Away from the CNS in peripheral nerves
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Macule
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Virus replication in the dermis, leads to a flat reddened lesion, created by long term vaso dilation in that area
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Papule
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A raised macule (raised due to local inflammation and edema)
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Vesicle
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Virus replication moved from the dermis to the epidermis, resulting in a small circumscribed epidermal elevation that contains clear fluid (like a blister)
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Pustule
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A vesicle with massive neutrophil infiltration. May or may not progress to scab formation.
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At what phase do Rb and p53 proteins work?
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G1 phase
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what aer examples of virus induced skin tumors?
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Warts, myxomatosis
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What percent of URI are casused by viruses?
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90%
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What does viral damage to epithelial cells release (that helps bacteria)
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iron.
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What type of cells in the intestine are relatively resistant to viral infection?
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Cuboidal cells
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what is the most common mode of spread for CNS infections
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Hematogenous spread. this means it occurs through the blood brain barrier, and the blood cerebrospinal fluid barrier
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what layer of the endothelium is responsible for preventing clot flormation on the walls?
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Glycocalyx-thrombomodulin
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Factor XII
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Hageman Factor
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Platelet adhesion to the subendothelial collagen is mediated by what?
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Von willebrand factor
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DIC stands for what?
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Disseminated intravascular coagulation
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Teratogenic viruses
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Cause birth defects and baby badness
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In long term infections, how is the virus shed?
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Can be intermittent or continous
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Epidemiology
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The branch of science that studies the frequency, distribution, and determinants of a disease in a population
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Arbo virus
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Arthropod borne viruses. These will multiply in the arthropod before being transmitted
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Cases
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Those animals suffering from a clinically diagnosable disease
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Case-fatality rate
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The number of deaths within the animals that are clinically ill
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Dead end host
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A host that is not involved with maintaining a virus.
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Field isolate
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The fresh virus isolate from it's natural host
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Vehicles of transmission (not fomites)
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air, food, milk, water
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Incidence
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the number of new cases in a given period of time
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Wild-type virus
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The original strain of a virus that is circulating in nature from which mutants arise
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Droplet transmission
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Particle of infected moisture goes no further than 1 meter (ie a sneeze)
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Airborne transmission
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Particle of infected moisture that moves further than 1 meter (it a sneeze that was picked up by the wind)
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