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60 Cards in this Set

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name: extracellular form of the virus
virus particle OR virion
what surrounds viral genome?
capsid
sometimes lipid-bilayer envelope
t/f: viruses replicate within the host
t
t/f: viruses adapt within the host
t
t/f: viruses are obligate intracellular parasites
t
t/f: measles, mumps, common cold are diseases caused by viruses
t
give 3 viral enzymes used as molecular biology tools
DNA ligase
reverse transcriptase
RNA polymerases
RNase H
what sets viruses apart from cells in terms of genome replication?
they can use RNA as a genome, or use ssDNA as a genome
what are viruses used for in the context of gene therapy?
to xfer genes into cells
size range of viruses
28nm (poliovirus) - 200nm (smallpox)
why does it make sense for capsids to be formed from many copies of the same protein?
limited size => limited genome coding capacity
name: protein coat directly surrounding genome
capsid
what is the nucleocapsid?
the nucleic acid and capsid complex
name: lipid bilayer and associated glycoproteins surrounding many types of nucleocapsids
envelope
name: the entire virus particle
virion
t/f: DNA and RNA are sometimes found together within the virus capsid
f
where does the virus envelope come from?
previous host
what are the three viral morphologies?
helical, spherical, complex
what shape are 'spherical' viruses technically?
icosahedron
t/f: some viruses contain a genome and enzymes within the capsid
t - may need enzymes to initiate replication cycle
t/f: viruses are capable of reproduction
f - the term replication is used because of the host dependency
length of typical animal virus replication cycle
8-24hr
name: the receptor on the virus used for attachment
anti-receptor
name: the receptor on the host cell that the virus binds to
virus receptor
what two factors determine host range?
presence of a viable receptor (susceptible)

presence of proper intracellular factors
(permissive)
cell types that a virus can infect (enter) are ___
susceptible
cell types that a virus can replicate in are ___
permissive
t/f: virus attachment is energy dependent
f
t/f: virus entry is energy dependent
t
define: (+) strand RNA
RNA that is immediately translatable (functionally equivalent to mRNA)
t/f: the (+) and (-) strands are complementary
t
t/f: some viruses contain segmented genomes (several molecules of RNA)
t
In eukaryotic cells, where are the DNA and RNA polymerases located?
nucleus
Eukaryotic mRNAS are modified with a ___ cap at the 5' end and a ___ tail at the 3' end. Why is this a problem for viruses?
methylated guanine, poly-A
this is a problem because many viral mRNAs lack these structures and must out-compete cellular mRNA for translation
t/f: virus assembly is an energetically unfavorable process
f
t/f: capsid assembly relies on inherent protein affinities
t
RNA-dependent RNA polymerases do what?
synthesize the complementary strand of RNA using viral RNA as template
t/f: all DNA viruses use the host DNA polymerase to replicate thier viral DNA
f - some provide thier own DNA polymerases
define retrovirus
RNA virus that uses reverse transcriptase to synthesize a single strand
name: virus release
egress
what are the possible ways for virus to leave the cell?
cell lysis
budding
t/f: cell lysis is used by enveloped viruses
f
most non-enveloped viruses leave the cell by ___
lysis
enveloped viruses leave the cell by ___
budding
during budding, what three places can the virus acquire an envelope from?
as it extrudes out of nucleus
OR
intracellular vesicle
OR
plasma membrane
t/f: budding is always harmful to the cell
f
t/f: all enveloped viruses modify the lipid envelope by inserting viral proteins
t
t/f: all virions must enzymatically cleave structures on the cell to free themselves during egress
f - only some (ie influenza)
enveloped viruses modify the envelope by inserting viral proteins during egress. What are these used for?
attachment
what four characteristics are used in the 'classic' classification system for viruses?
nature of nucleic acid
symmetry of capsid
presence of envelope
dimensions of virion / capsid
t/f: type of disease a virus caused is used to classify viruses
f
how does the Baltimore system classify viruses?
based on the genetic system of each virus, and the relation between genome and production of mRNA
t/f: the classical and Baltimore system are mutually exclusive
f
t/f: studies of viral replication require the growth (cultivation) of host cells
t
what are the two types of cell culture?
primary
tumor
to make a primary cell culture, animal tissue is treated with ___ to dissociate the cells
trypsin
t/f: primary cell culture is immortal
f - after only a few rounds of division they will die
define 'in vitro'
in glass (test tube)
define 'in vivo'
in the body
What four viruses have been linked to cancer?
Epstein-Barr -> Burkitt's lymphoma (tumor of jaw and abdomen)
Hepatitis B (some liver cancers)
Papillomaviruses (cervical cancer in women)

two retrovirus (HTLV-1 and -2: T cell leukemia)