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a virus that infects prokaryotic cells
bacteriophage
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a protein shell that surrounds teh genome of a virus particle
capsid
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a subunit of a capsid
capsomer
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a virus that relies on another virus, the helper virus, to provide some of its components
defective virus
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a protein synthesized soon after virus infection and before replication of the virus genome
early protein
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a virus that provides some necessary components for a defective virus
helper virus
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cell inside which a virus replicates
host cell
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three-dimensional figure with 20 triangular faces
isosahedron
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a protein made later in viral infection, after replication of the virus genome
late protein
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a bacterium containing a provirus
lysogen
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a state following virus infection in which the viral genome is replicated as a provirus along with the genome of the host
lysogeny
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a series of steps after virus infection that leads to virus replication and teh destruction (lysis) of the host cell
lytic pathway
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a virus with a single stranded genome that has teh opposite sense to (is complimentary to) the viral mRNA
negative-strand virus
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a zone of lysis or cell inhibition caused by virus infection of a lawn of sensitive cells
plaque
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a virus with a single stranded genome that has teh same complimentarity as the viral mrNA
positive strand virus
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teh genome of a temperate virus when it is replicating in step with, and often integrated into, the host chromomse
provirus/prophate
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a virus whose RNA genome has a DNA intermediate as part of its replication cycle
retrovirus
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the process of copying information found in RNA into dna by teh enzyme reverse transcriptase
reverse transcription
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a virus whose genome is able to replicate along with that of its host withoug causeing cell death in a state called lysogeny
temperate virus
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virion
infectious particle; the nucleic acid genome surrounded by a protein coat and in some cases other layers of material
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a virus that lyses or kills the host cell after infection; a non temperate virus
virulent virus
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a genetic element containing either rna or dna surrounded by a protein capsisd and that replicates only inside host cells
virus
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small circular single strandecd rna that causes certain plant diseases
viroid
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nucleic acid surrounded by protein
extracellular
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inert. doesnt carry out respiration or biosynthesis. how they move from cell to cell
virion
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most viruses are either linear or circular
linear
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overall viral assembly is a a what assembly
self assembly
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nucleic acid + protein packaged in virion
nucleocapsid
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layers around a nucleocapsid
envelope
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the way in which capsomers are arranged in virus capsid
symmetry
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2 types of symmetry
rod and spherical
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-
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which is more efficient, spherical or rod?
spherical, icosahedral
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lipid bilayer + glycoproteins makes inital contact with the cell
viral envelope
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icosahedral head + tails. tail is complex, composed of many proteins
complex virus
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makes a small hole in cell wall. so nucleic acid can enter. made in later stages of infection causes lysis
lysozyme.
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number of infectious units per volume of liquid
titer
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a zone of lysis: clear area. replication of a virion. is formed when cells are lysed
plaque
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How do you do a plaque assay?
virus partciles are mixed with host bacterial and spread on a nutrient agar medium and then incubated adn then count the number of plaque forming units
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know how concentrated a viral suspension needs to be to yield a certain number of plaques
efficiency of plating
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5 steps for viral replication
- 1. attachment of virion to host cell
- 2. penetration of virion or nucleic acid
- 3. synthesis of virus nucleic acid and protein
- 4. assembly of capsids and packaging of viral genomes
- 5. release of mature virions
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What happens in the 1st few minutes of infection?
eclipse: infectious particles cant be detected since they are absorbed into host cells viral nucleic acid enters.
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begins as nucleic acids are packaged into protein coats. titer rises. virus particles still cant be detected
maturation
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eclipse + maturaiton
latent period
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mature virions can be released by what 3 ways?
lysis/budding/excretions
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number of virions released
burst size
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how does T4 infect a cell?
- 1. attach cell fibers
- 2. then retract and core makes contact with cel wall with tail pins
- 3. lysozyme forms small pore in peptidoglycan
- 4. tail sheath contracts and injects dNA
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cleaves viral DNA to prevent replication (restriction)
restriction endonucleases
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how do viruses protect DNA?
methylation and glucosylation so it prevents restriction endonucleases attack
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what configuration for mRNA must all viruses have?
+
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semi conservative; dsDNA(+ or -)
class I
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semi conservative (ssDNA +) make of other strand---ds intermediate---discard one-----transcription
class II
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ds RNA +, transcribe the minus strand
class III
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ssRNA (+) used directly as mrna
class IV
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transcription of minus strand of ssrna (-)
V
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ssrna + retrovirus, reverse transcriptase, ds dna intermediate ---transcritption of - strand
class VI
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ds dna (+ or -), transcription followed by reverse transcription
class VII
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soon after infection, help with replication of virus nucleic acids and are made in smaller amounts
early proteins
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make the protein coat, more structural and made in large amounts
late proteins
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several genomic units end to end to make a long dna molecule
concameter
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enzymes needed dna rep and transcription
early and middle proteins
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proteins of head and tail and liberate phages
late proteins
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recognizes dna sequences in middle promoters and guides them to rna pol
mot A
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lysogens
HARBOR TEMPERATE VIRUSES
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types of lysogenti viruses
lambda and p1
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helps inactivate lytic pathway
repressor proteins
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cro proteins
lytic pathway
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2 things must happen so lytic pathway does not happen
- 1? synthhesis of late proteins must be stopped
- 2. copy of lambda dna must be integrated in host chromosome
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