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84 Cards in this Set
- Front
- Back
T or F viruses are infectious agents too small to be seen by the light microscope
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True. viruses are infectious agents too small to be seen by the light microscope
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T or F viruses are 5000 fold smaller than the cells they infect
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False. Viruses are 100 - 1000 fold smaller than the cells they infect
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T or F viruses are true cells
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False. Viruses are NOT true cells
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T or F viruses are obligate intracellular parasites
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true. viruses are obligate intracellular parasites
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T or F virions can contain RNA and DNA
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False. Virions contain only RNA or DNA. Never both
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Because of the small size of a virus, they contain little nucleic acid and very few ___
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Because of the small size of a virus, they contain little nucleic acid and very few genes
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T or F viruses are living organisms
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False. Viruses are NON-Living
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Viruses can infect what types of things?
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animals, plants, and other microorganisms
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define bacteriophage
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viruses that infect only bacteria
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define phage
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same as bacteriophage - viruses that infect only bacteria
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the size of a virus is measured in ____. most viruses range in size from ___ to ____
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the size of viruses is measured in nanometers (nm). most are between 10nm to 500nm
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Viruses contain (a) protein, DNA or RNA (b) protein, DNA, and RNA, (c) just protein (d) DNA
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A. protein, either DNA or RNA
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Viruses are totally dependent on _____ for replication
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host cell
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viral components must assemble into _____ in order to go from one host cell to another
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complete viruses
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another name for complete virus
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viroid
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shapes of viruses?
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isometric, helical, complex
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isometric virus
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isometric - nucleic acid surrounded by a polyhedral (many shape) shell or capsid (ex: adenovirus)
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helical virus
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ribbon like consist of nucleic acid surrounded by a hollow protein cylinder or capsid. possess a helical structure (ex tobacco mosaic virus)
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complex virus
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polyhedral head and helical sheath or tail; (ex: most phages)
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viruses will be either naked capsid or an envelope morphology. what does "naked virus" mean?
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naked viruses have protein capsids and nucliec acid. they are resistante and survive in the outside world
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what is enveloped virus
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envelope virus has a capsid, nucleic acid, and an envelope. they are susceptible to environmental factors such as drying, gastric acidity and bile
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T or F a capsid is a protein coat
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true
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T or F the shape of the virus is determined by the shape of the capsid
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true
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capsids are found in how many viruses? (a) most (b) a few (c) not many
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capsids are found in most viruses
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capsomere
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capsomeres are protein subunits; capsids are made of capsomeres
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capsids purpose?
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serves to PROTECT and INTRODUCE viral genome into host cell
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define nucleocapsid or naked virus
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viruses consisting of a genome surrounded by a capsid
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T or F attachment proteins project out from the capsid and bind the virus to host cells
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true
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Most animal viruses have ___
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an envelope
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a virus' envelope is similar to
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eukaryotic cell membrane; composed of a lipid bilayer
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where is an envelope derived from?
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derived from host cell membranes by a process called budding
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T or F enevlopes are usually of host cell origin; but the virus does incorporate proteins of its own, often appearing as glycoprotein spikes
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True
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the glycoprotein spikes function in ?
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spikes function in attaching the virus to receptors on susceptible host cells
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the nucleic acid of a virus will be what type? DNA or RNA?
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either a DNA or RNA
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the nucleic acid of a virus will be what type? single stranded, double stranded?
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single or double stranded
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the nucleic acid of a virus will be what type? linear, circular, or segmented?
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can be circular, segmented, or linear
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the nucleic acid of a virus will code for?
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codes for the synthesis of viral components and viral enzymes for replication
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T or F Viruses contain many enzymes in their capsid
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False. Viruses contain a few enzymes in their capsid
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Are the enzymes of viruses active or inactive? When does the inactive or active state of a virus change?
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Enzymes of viruses are inactive. They become active after the virus has entered the host cell
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What Enzyme does the HIV virus carry?
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HIV carries Reverse Transcriptase -- a RNA dependent DNA polymerase
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Animal Viruses: type of nucleic acid and its arrangement?
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animal viruses: DNA or RNA; single or double stranded; linear or segmented
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replication scheme for animal viruses?
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Lytic, Temperate, replication may occur in the nucleus or cytoplasm
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shapes of animal viruses
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spherical, rod, complex
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T or F animal viruses are not enveloped, only naked
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False. Animal viruses can be enveloped or naked viruses
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what is the replication cycle for viruses
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multiply in host cell only; uses host cell structures and enzymes; contains little nucleic acid
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the little nucleic acid that the virus contains, what is it used for?
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used to make the viral protein coat; assures replication of viral nucleic acid; moves the virus into and out of the host cell
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the replication cycle exists in two phases, inside the cell and outside the cell. explain
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outside the cell -- metabolically inert; inside the cell -- replication form
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in what ways can viruses be transmitted?
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inhaled ddroplets, food/water, direct transfer from other infected hosts, bites of vector, transplacental, sexually transmitted
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T or F viruses can infect only one or a restricted range of host species
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true
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T or F with viruses, there is a specific interaction between the nucleocapsid or virus membrane and host molecules
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true
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what are the types of relationships a virus can have with a host cell
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productive infection, extrude, latent infection, lysogenic cell
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define productive infection
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multiply inside the host cell and cause lysis phage -- called virulent phage or lytic phage
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define extrude
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some viruses leak out of the host cells w/o killing them
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with latent infection, the virus becomes a part of the genome of the host cell. T or F
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true
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define temperate phage
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due to latent infection; modify properties of the host cell phage
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define lysogenic cell
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a phenomenon called lysogenic conversion bacterial cell carrying a prophage is called lysogenic cell
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what are the stages of viral replication
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attachment, penetration, transcription, replication of phage DNA and synthesis of protein, assembly, release
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attachment phase
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virus must bind to specific receptor on surface of host cell
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penetration phase
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after few minutes, enzyme in the tip of the phage tail degrades small portion of the bacterial cell wall and the DNA is injected into the cell while protein coat of the phage remains on the outside
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transcription
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phage DNA in the host cell is transcribed into mRNA which is then translated into protein
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replication of phage DNA and synthesis of protein
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phage protein and nucleic acid replicate independently of one another.
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DNA from replication phase serves as two functions. What are they
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template for replication of more phage DNA, template for synthesis of mRNA
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assembly
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assembly or maturation process forms intact or mature phage. Once the phage head is formed it is packed with DNA. The tail is then attached, followed by the addition of tail spikes
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release
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enzyme lysozyme is synthesized to digest host cell from within; this results in cell lysis and the release of the phage
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with generalized transduction, can any bacterial gene be transferred?
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yes, any bacterial gene can be transferred.
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what types of phages carry out generalized transduction?
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generalized transducing phages carry out generalized transduction
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which types of phages serve as generalized transducing phages?
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virulent and temperate phages
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with generalized transduction, what happens?
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DNA from donor cell integrate into the recipient cell DNA by homologous recombination
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specialized transduction - what types of genes transfer?
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only a few specific genes
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what carrys out the specialized transduction?
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temperate phages ONLY (NOT virulent)
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with specialized transduction, a peice of bacterial DNA remains attached to the peice of phage DNA that is exised. T or F
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true
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with specialized transduction, when does the phage DNA replicate
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the phage DNA and the bacterial gene attached to the phage DNA replicate at the same time
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what genes are transduced with specialized transduction?
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Only genes located near the site at which the temperate phage integrates its DNA are transduced
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define balanced pathogenicity
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most viruses infect and persist within the hose in a state of BALANCED PATHOGENICITY in which the host is not killed
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viruses cause diseases classified as:
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acute or persistent
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define acute infetions
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acute infections: short duration, self-limited, virus is localized, may lead to lasting immunity (ex: measles, mumps, influenza, poliomyelitis)
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define persistent infections
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persistent infections can be: late complications following an acute infection, latent infection, chronic infection, slow infections
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Interactions of animal viruses with their hosts?
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attachment, entry, target site of viral replicaiton, uncoating, replication of nucleic acid and protein, maturation, release, shedding, transmission,
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when animal viruses interact with their host and attachment occurs, what does that mean
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fusion of viral envelope and host membrane
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where is viral replication in the host of an animal virus?
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either nucleus or cytoplasm
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what is uncoating
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in all viruses, nucleic acid separates from its protein prior to the start of replication
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in the maturation stage of animal virus, what happens
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protein formation occurs, protein coat and nucleic acid are assembled
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in the "release" stage of animal virus, what happens
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cell lysed; budding in persistant infection, or exocytosis
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shedding?
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shedding occurs from the same opening or surface that the virus enters from mucus, saliva, feces, etc
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