final part 5
Medical Microbiology 463 with Kahlife at Michigan State University
About this deck
By: Kara Brockhaus
Created: 2010-12-02
Size: 111 flashcards
Views: 40
Created: 2010-12-02
Size: 111 flashcards
Views: 40
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why study viruses?
1. viruses infect and often cause diseases
2. simple genetic systems that allow us to study basic
biochemical mechanisms
3.obligate intracellular parasites
4.they have evolved fascinating and varied life cycles
2. simple genetic systems that allow us to study basic
biochemical mechanisms
3.obligate intracellular parasites
4.they have evolved fascinating and varied life cycles
bc viruses are intracellular parasites they use _____ express their genes, replication and form ___
host cell machinery
virions
virions
Several important scientific advances were made using viruses:
RNA splicing,
first in vitro DNA replication system,
first completely sequenced genome
first in vitro DNA replication system,
first completely sequenced genome
first sign of virus vaccines?
china 1000AD
viruses contain a limited genomic structure
surrounded by a modest ____ and
(in some) a ____ envelope
surrounded by a modest ____ and
(in some) a ____ envelope
protein capsid
lipo-protein
lipo-protein
viruses are ___ and ____
sub-microscopic
obligate intracellular parasites
obligate intracellular parasites
what do viruses lack?
organelles, cellular organization, and
cellular metabolic mechanisms
cellular metabolic mechanisms
are viruses smaller or bigger than bacteria?
smaller
(10-100nm)
(10-100nm)
what are the 4 basic shapes of viruses?
tobacco mosaic virus
adenovirus
influenza virus
bacteriophage T$
*KNOW THESE SHAPES*
adenovirus
influenza virus
bacteriophage T$
*KNOW THESE SHAPES*
classification of viruses is important in understanding
virus replication
virus genomes can be
ss RNA
ds RNA
ds DNA
ssDNA
ds RNA
ds DNA
ssDNA
virus genomes can encode as few as
3-5 proteins
___ growth dynamics of viral reproduction
compared to____ increase in bacterial
numbers
compared to____ increase in bacterial
numbers
Step-wise
smooth, curvilinear
smooth, curvilinear
during a latent period what happens?
no infectious viruses are present
stages of virus replication
absorption
eclipse (replication and transcription)
maturation phase
release
eclipse (replication and transcription)
maturation phase
release
virion def
the completely assembled, infectious virus
particle
particle
capsid def
the protein coat (consisting of individual
capsomeres) surrounding the genome
capsomeres) surrounding the genome
genome def
the viral nucleic acids (DNA or RNA)
envelope def
a lipoprotein matrix of both host cell
and virus derived sources
and virus derived sources
replication def
the process by which a virus copies
its own genome, synthesizes capsomeres, and
assembles the genome in the capsid
its own genome, synthesizes capsomeres, and
assembles the genome in the capsid
titer -noun def
the number or density of viruses per
unit volume of medium (e.g., serum)
unit volume of medium (e.g., serum)
titer -verb- def
the procedure of determining the
number of infectious units or plaque forming units
in a suspension of virus. Generally expressed in
logarithmic units
number of infectious units or plaque forming units
in a suspension of virus. Generally expressed in
logarithmic units
plaque forming unit def
the amount or titer of virus
required to form one plaque in a cell culture
monolayer (abbreviation, pfu)
required to form one plaque in a cell culture
monolayer (abbreviation, pfu)
plague def
a “hole” in a cell culture monolayer
indicative of virus infection and cell lysis
indicative of virus infection and cell lysis
if viral envelope is present it consists of ...
host cell-derived cell membrane,
glycoproteins, and matrix proteins of either
host or virus origin
glycoproteins, and matrix proteins of either
host or virus origin
what are the 7 classes of viruses
ds DNA
ss DNA
ds RNA
ss RNA that can serve as mRNA
ss RNA that can serve as a template for mRNA
ss RNA that can serve as a template for DNA synthesis
hepadnavirus
ss DNA
ds RNA
ss RNA that can serve as mRNA
ss RNA that can serve as a template for mRNA
ss RNA that can serve as a template for DNA synthesis
hepadnavirus
examples of large viruses with size______
poxvirus
herpesvirus
*100-200 kb
herpesvirus
*100-200 kb
examples of small viruses with size___
papovaviruses,
parvoviruses
*5-10 kb
parvoviruses
*5-10 kb
variation for DNA
ss -circular/linear
ds - circluar/ linear
grapped circular
ds - circluar/ linear
grapped circular
variations for RNA
ss-circulare/linear
ds-circulare/linear
ds-circulare/linear
ss RNA ambisense
some positive and some negative sense strands
ss RNA may or may not be
segmented
ss RNA positive means...
“infectious,” may function as mRNA
ss RNA negative means...
“noninfectious,” must be copied to a +strand
The largest and most complex viruses are the
poxviruses
characteristics of poxviruses
*large (200-400 nm diam)
*double-stranded DNA genome with
150-300 kb encoding ca. 200 genes
*Virion incorporates 10 enzymes with DNA
replication functions
*double-stranded DNA genome with
150-300 kb encoding ca. 200 genes
*Virion incorporates 10 enzymes with DNA
replication functions
in a poxvirus, Extracellular virions have __envelope
membranes; intracellular virions have __
membrane from____
membranes; intracellular virions have __
membrane from____
2
one
golgi apparatus
one
golgi apparatus
characteristics of paravirus
• Single stranded DNA, 5 kb
• Virions are “naked” (no envelope)
• Virion is completely dependent on host cell
functions for replication and virion assembly
*Very small (18-26 nm diam; visible only with
electron microscopy)
• Virions are “naked” (no envelope)
• Virion is completely dependent on host cell
functions for replication and virion assembly
*Very small (18-26 nm diam; visible only with
electron microscopy)
Some parvoviruses cannot “__” host cell
DNA replication machinery, and require a__in coinfection for replication
DNA replication machinery, and require a__in coinfection for replication
turn on
helper virus
helper virus
Capsid consists of basic (___)
proteins which can encapsulate ____
nucleic acids comprising the genome
(=___)
proteins which can encapsulate ____
nucleic acids comprising the genome
(=___)
positively charged
negatively charged
nucleocapsid
negatively charged
nucleocapsid
The capsid consists of subunits called ___
that are individual proteins.
that are individual proteins.
capsomeres
Capsomeres assemble into capsids of two basic
shapes, forming the virion nucleocapsid:
shapes, forming the virion nucleocapsid:
– Helical capsids
– Icosahedral capsids
– Icosahedral capsids
The helix in helical capsids are defined by two parameters in
the equation, the ___, and
the __
the equation, the ___, and
the __
pitch
amplitude or diameter
amplitude or diameter
pitch=
υ x p,
υ =
the number of
subunits/turn
subunits/turn
example of helical capsid structure virus
tobacco mosaic virus
example of isoahedral capsid strucutre visurs
adenovirus
Icosahedrons are __-sided and 3D
20
isoahedrals have each face being an
equilateral triangle
(with 12 corners)
(with 12 corners)
the min. one capsid can have in an isoahedral capsid is capsomeres
60
flavivirus structure
presence of a
host-cell derived
lipid envelope
around the
nucleocapsid
host-cell derived
lipid envelope
around the
nucleocapsid
herpesvirus is An __ enveloped with ___
after exiting the host cell by exocytosis or lysis
after exiting the host cell by exocytosis or lysis
icosahedral virion
host cell nuclear membrane
host cell nuclear membrane
viral envelope also contains
viral-encoded proteins
Many enveloped virions exit the host cell by
___ as the envelope when it is acquired, thus
they ___ the host cell.
___ as the envelope when it is acquired, thus
they ___ the host cell.
budding
do not kill
do not kill
Some virions that
acquire an internal envelope exit host via
acquire an internal envelope exit host via
lysis or exocytosis
lipid membrane of viral envelope is composed from ___ and made out of___
host cell lipids
*May be derived from host cell plasma membrane, from
nuclear membrane, or from Golgi membrane
*May be derived from host cell plasma membrane, from
nuclear membrane, or from Golgi membrane
nonenveloped viruses do what when leaving the cell?
lyse host cell ---= kill cell
What do the virion-encoded proteins do?
– Protect nucleic acid
– Attach to receptors on cells: host cell binding
– Penetrate cell membrane
– Replicate nucleic acid (some)
– Begin program for replication (some)
– Modify host cell (some)
– Attach nucleocapsid to envelope
– Attach to receptors on cells: host cell binding
– Penetrate cell membrane
– Replicate nucleic acid (some)
– Begin program for replication (some)
– Modify host cell (some)
– Attach nucleocapsid to envelope
ebola is a ___virus and is in what shape?
filovirus
helical
helical
rabies is a ___virus and is in what shape?
rhabdovirus
helical
helical
Togavirus is in what shape?
icosahedral
Virus classification
• Classify into groups (=taxa) based upon
• Classify into groups (=taxa) based upon
common physical/chemical properties
viruses in same group often have similar
biological properties
– Replication
– Disease
– Spread
– Replication
– Disease
– Spread
Classify by course of disease and pathology
is problematic, because unrelated viruses
may cause
is problematic, because unrelated viruses
may cause
similar symptoms and have
similar routes and courses of infection
similar routes and courses of infection
what viruses could cause symptoms for Meningoencephalitis
rabies
(Rhabdoviruses), herpesviruses,
flaviviruses, bunyaviruses, etc.
(Rhabdoviruses), herpesviruses,
flaviviruses, bunyaviruses, etc.
what viruses could cause symptoms for Hemorrhage with fever:
filoviruses (Ebola),
yellow fever and dengue viruses
(flaviviruses)
yellow fever and dengue viruses
(flaviviruses)
what viruses could cause symptoms for respiratory disease
Adenoviruses,
Orthomyxoviruses, Paramyxoviruses, some
Herpesviruses
Orthomyxoviruses, Paramyxoviruses, some
Herpesviruses
what viruses could cause symptoms for diarrhea
Reoviruses, Coronaviruses,
Pestiviruses, …
Pestiviruses, …
classification schemes for viruses are based upon
Genome
• Morphology of virion, envelope
• Replication strategy
• Antigenic and serological relationships (Serotypes)
• Physicochemical properties
• Protein, lipid, and carbohydrate content
• Biological properties
• Morphology of virion, envelope
• Replication strategy
• Antigenic and serological relationships (Serotypes)
• Physicochemical properties
• Protein, lipid, and carbohydrate content
• Biological properties
old classification of viruses from andre lwoff
• Genome is RNA or DNA
• Symmetry of the capsid (helical or icosahedral)
• Presence or absence of an envelope
• Dimensions of the virion and capsid
• Symmetry of the capsid (helical or icosahedral)
• Presence or absence of an envelope
• Dimensions of the virion and capsid
order of viruses?
virales
family of viruses?
viridae
genera of viruses?
virus
species of viruses?
uncommon assignment;
virtually never used but species as a
category is used more and more)
virtually never used but species as a
category is used more and more)
strain name of viruses is often
a number or
alphanumeric
alphanumeric
common name of viruses is often
the place of origin or
some other general descriptor
some other general descriptor
def of hepdnavirus
DNA
viruses that have an RNA
intermediate
viruses that have an RNA
intermediate
• Class I:
DS DNA genome
• Class II:
SS DNA genome
• Class III:
DS RNA genome
• Class IV:
Positive SS RNA genome
• Class V:
Negative SS RNA genome
• Class VI:
Positive SS RNA genome with reverse
transcription to DNA
transcription to DNA
• Class VII:
Double-stranded DNA with RNA
intermediate
intermediate
Poxviruses
replicate in the
replicate in the
cytoplasm
Class I examples
adenoviruses,
herpesviruses, poxviruses.
papillomaviruses, chicken pox virus
herpesviruses, poxviruses.
papillomaviruses, chicken pox virus
class one tend to replicate in___except for __
nucleus
pox
pox
examples of class 2
Human parvovirus, circoviruses
how is class three replicated?
genome is
segmented into pieces; each segment is
transcribed separately into monocistronic
(“stand alone”) RNA transcripts and copies
segmented into pieces; each segment is
transcribed separately into monocistronic
(“stand alone”) RNA transcripts and copies
how is class two replicated?
+sense DNA genome:
replication occurs in the nucleus, involving
formation of a –sense strand, which serves
as template for +strand for RNA and DNA
synthesis
replication occurs in the nucleus, involving
formation of a –sense strand, which serves
as template for +strand for RNA and DNA
synthesis
examples of class 3
(Reoviruses; Birnaviruses)
• Blue tongue virus, Epizootic Hemorrhagic
virus (deer), Colorado tick fever virus,
rotaviruses (diarrhea in children)
• Blue tongue virus, Epizootic Hemorrhagic
virus (deer), Colorado tick fever virus,
rotaviruses (diarrhea in children)
class 4 has what two types?
(1) polycistronic (genes together) messenger
RNA that is infectious as is
(2) Complex two step transcription
RNA that is infectious as is
(2) Complex two step transcription
class 4 polcistronic has no ___associated with polymerase
virion
def of class 4 polycistronic
Translation
results in formation of a polyprotein product
which is cleaved to form subunit proteins
results in formation of a polyprotein product
which is cleaved to form subunit proteins
examples of class 4 polycistronic
Picornaviruses; hepatitis A virus
examples of class 4 complex two step transcription
togaviruses
what is needed in class 4 complex two step transcription?
Two or more rounds of
translation are necessary to produce viral
genomic RNA.
translation are necessary to produce viral
genomic RNA.
most important class 4 examples
Coronaviruses
Picornaviruses
Caliciviruses
Flaviviruses
Togaviruses
Picornaviruses
Caliciviruses
Flaviviruses
Togaviruses
class 5 must have...
a
virion particle associated RNA polymerase
virion particle associated RNA polymerase
class 5 is broken into whta two types?
(1) segmented
(orthomyxoviruses): replication of the
–sense RNA to monocistronic +mRNA via
RNA polymerase
(2) Nonsegmented
(rhabdoviruses).
(orthomyxoviruses): replication of the
–sense RNA to monocistronic +mRNA via
RNA polymerase
(2) Nonsegmented
(rhabdoviruses).
class 5 examples
ebola
Marbrg
rabies
arenaviruses
influenza
Parainfluenza viruses
Marbrg
rabies
arenaviruses
influenza
Parainfluenza viruses
examples of class 6
HIV, HTLV
class 6 replication methods
reverse
transcription of RNA to DNA intermediate,
forming a provirus which integrates into the
host cell genomel.
transcription of RNA to DNA intermediate,
forming a provirus which integrates into the
host cell genomel.
class 6 requires what?
viral-encoded
reverse transcription enzyme.
reverse transcription enzyme.
class 7 replication strategies
production
of RNAs, followed by reverse transcription
of RNA to DNA intermediate inside the
virion.
of RNAs, followed by reverse transcription
of RNA to DNA intermediate inside the
virion.
class 7 does not do what?
integrate into the host genome
upon infection of new cell in class 7 the first event is repair of ____followed by___
gapped genome
transcription
transcription
example of class 7
hep b
About this deck
By: Kara Brockhaus
Created: 2010-12-02
Size: 111 flashcards
Views: 40
Created: 2010-12-02
Size: 111 flashcards
Views: 40
About StudyBlue
STUDYBLUE makes things that make you better at school.
Things like online flashcards with photos and audio.
Things like personalized quizzes and friendly reminders about when (and what) to study next.
Think of it as a digital backpack™: access to all of your study materials online and on your phone.
STUDYBLUE exists to make studying efficient and effective for every student, for free. Join us.
“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy
Kathy