3. Structure and Composition

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Lecture 2

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111 Terms

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Pleomorphism
A virus’ ability to alter its shape or size
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400nm
Diameter of the largest viruses
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17nm
Diameter of the smallest viruses
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Capsid
Protein shell of a virus. Encases viral nucleic acid/genome. Composed of basic subunit proteins called capsomeres.
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Capsomeres
Capsids are composed of _________ held together by non-covalent bonds.
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Non-covalent
Capsids are composed of capsomeres held together by ___________ bonds.
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nucleocapsid
Capsid + Viral Nucleic Acid/Genome =
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Helical
Type of symmetry in which capsomeres and nucleic acid are wound together to form a spiral tube.
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True
TRUE/FALSE: In all animal viruses, the helical nucleocapsid is enclosed within a lipoprotein envelope.
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False
TRUE/FALSE: In all plant viruses, the helical nucleocapsid is enclosed within a lipoprotein envelope.
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Cannot
Due to interactions between nucleic acid and capsid proteins, incomplete virions - empty helical particles - (CAN/CANNOT) form.
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Icosahedral
Type of symmetry present in spherical viruses.
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Cubic
Icosahedral symmetry is also called __________ symmetry.
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Pentons, vertices
Icosahedral capsids are composed of ________ (pentagonal capsomeres) at the ___________, and hexons (hexagonal capsomeres) for the facets.
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Hexons, facets
Icosahedral capsids are composed of pentons (pentagonal capsomeres) at the vertices, and ________ (hexagonal capsomeres) for the _______.
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12, 20, 30
An icosahedron has (*#)* corners/vertices, (#) facets (triangular faces), and (#) edges.
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12
There are always (#) pentons in a spherical virus.
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True
(TRUE/FALSE): The number of hexons varies between spherical viruses.
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False
(TRUE/FALSE): The number of pentons varies between spherical viruses.
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pentagons
The T-number describes the relation between the number of __________________ and hexagons of the icosahedron.
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hexagons
The T-number describes the relation between the number of pentagons and _____________ of the icosahedron.
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triangulation
The “T” in “T-number” stands for
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H
The formula for the triangulation (T) -number is

T = __^(2) + h \* k + k^(2)
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h
The formula for the triangulation (T) -number is

T = h^(2) + __ \* k + k^(2)
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k
The formula for the triangulation (T) -number is

T = h^(2) + h \* __ + k^(2)
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k
The formula for the triangulation (T) -number is

T = h^(2) + h \* k + __^(2)
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distances
In the formula for T-number, h and k are the _____________ between successive pentagons on the virus surface per axis.
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simple
Parvovirus has a T value of 1. It is the most (SIMPLE/COMPLEX) icosahedron.
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reoviridae
______________ has two capsids with different T-numbers.
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family
\*REVIEW: The name “Reoviridae” describes a(n): (ORDER/FAMILY/SUBFAMILY/GENUS/SPECIES).
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genus
\*REVIEW: The name “Parvovirus” describes a(n): (ORDER/FAMILY/SUBFAMILY/GENUS/SPECIES).
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1
The parvovirus T-number is =
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2
The outer capsid of Reoviridae has a T=13 icosahedral symmetry, while the inner has a T=___.
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13
The outer capsid of Reoviridae has a T=____ icosahedral symmetry, while the inner has a T=2.
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reoviridae
The outer capsid of ______________ has a T=13 icosahedral symmetry, while the inner has a T=2.
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complex
Virions are composed of several parts with separate shapes and symmetries. This includes Pox viruses and bacteriophages. They have _____________ symmetry.
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symmetry
The viral capsid is responsible for the structural ___________ of the virus particle.
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nucleic acid
The viral capsid encases and protects the viral _________ ________ from enzymes, chemicals, and physical conditions.
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attachment
The receptor attachment proteins on a viral capsid facilitate the ______________ of the virus to specific receptors on susceptible host cells.
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receptors
The receptor attachment proteins on a viral capsid facilitate the attachment of the virus to specific _________ on susceptible host cells.
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host cells
The receptor attachment proteins on a viral capsid facilitate the attachment of the virus to specific receptors on susceptible __________ ___________.
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cell membranes
The viral capsid aids in interaction with the host ___________ ___________ to form the envelope.
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uncoating
The viral capsid aids in _______________ of the genome in the host cell.
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viral genome
The viral capsid aids in transport of the __________ __________ to the appropriate site.
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packaging
The viral capsid facilitates specific recognition and ____________ of the nucleic acid genome.
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antigenicity
The viral capsid can contribute to the ____________ of the virus, being targeted by and binding to antibodies.
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lipid bilayer
Virus envelopes are usually a _____________ _____________ with embedded proteins.
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proteins
Virus envelopes are usually a lipid bilayer with embedded ________________.
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budding
The process by which a virus acquires an envelope.
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matrix protein
There are two kinds of viral proteins typically found in an envelope: glycoprotein and __________ _____________.
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glycoprotein
There are two kinds of viral proteins typically found in an envelope: ____________ and matrix protein
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external glycoproteins
Virus envelope glycoproteins may be either ____________ ______________, anchored into the envelope, or channel proteins, hydrophobic proteins altering the permeability of the membrane.
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channel proteins
Virus envelope glycoproteins may be either external glycoproteins (anchored into the envelope) or ___________ ____________ (hydrophobic proteins altering the permeability of the membrane).
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antigens
External glycoproteins are typically major _____________ of the virus. They also contribute to hemagglutination, receptor binding, and membrane fusion.
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internal environment
Channel proteins alter the permeability of the viral membrane, helping to modify the ___________ ____________ of the virus.
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virus envelope matrix
__________ _________ _______ Proteins link the internal nucleocapsid to the lipid membrane envelope.
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assembly
Virus envelope matrix proteins play a crucial role in virus ____________
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nucleocapsid
The virus envelope matrix protein serves as the recognition site of ________________ at the plasma membrane.
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encapsidation
The virus envelope matrix protein mediates the ___________________ of the RNA-nucleoprotein cores into the membrane envelope.
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cytoplasmic membrane
The virus matrix protein coats the inside of the host cell’s ____________ ______________.
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host
The viral envelope is acquired from a cellular membrane of a ___________ cell.
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lipid envelope
The viral _________ ________ is maintained only in aqueous or moist environments.
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less
Enveloped viruses are (MORE/LESS) hardy than non-enveloped viruses.
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more
Enveloped viruses are (MORE/LESS) susceptible to sterilization than non-enveloped viruses.
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inactivated
Enveloped viruses can be ___________ by the dissolution of the lipid membrane with lipid solvents such as ether, chloroform, and detergents.
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cannot
Enveloped viruses (CAN/CANNOT) survive long periods in the environment.
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capsule
Which of the following is NOT a component of a virus

* nucleic acid
* capsid
* envelope
* capsule
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false
(TRUE/FALSE) The viral matrix protein is located between the viral nucleic acid and the capsid.
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true
(TRUE/FALSE): The viral matrix protein is located along the inside of the host cytoplasmic membrane
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DNA
Virus Nucleic Acids are typically either _____ or RNA.
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RNA
Virus nucleic acids are typically either DNA or ______.
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single
Viral nucleic acids - DNA/RNA - can be either double or ______ stranded.
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double
Viral nucleic acids - DNA/RNA - can be either single or __________ stranded.
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circular
Viral DNA can be linear or
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linear
Viral DNA can be either circular or
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sense
Viral RNA can be either (+) or (-)-_______________
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infectious
A (+)-sense RNA virus is a/n (INFECTIOUS/NONINFECTIOUS) genome.
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noninfectious
A (-)-sense RNA virus is a/n (INFECTIOUS/NONINFECTIOUS) genome.
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translated
The positive-sense RNA virus is similar to mRNA and can be immediately ___________ by the cell.
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converted
Negative-sense viral RNA is complementary to mRNA and must be ____________
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drift
Viruses can undergo antigenic _______ or antigenic shift
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shift
Viruses can undergo antigenic drift or antigenic _______
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antigenic drift
Mechanism of viral genetic diversity resulting in mutations.
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antigenic shift
Mechanism of viral genetic diversity resulting in recombination and reassortment
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Missense
Point mutations can be

* silent
* nonsense
* __________
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nonsense
Point mutations can be

* silent
* ___________
* missense
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silent
Point mutations can be

* ____________
* nonsense
* missense
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recombination
The exchange of nucleotide sequences between different, but usually closely related, viruses during replication.
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reassortment
The most important mechanism for genetic diversity in viruses with segmented genomes
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true
(TRUE/FALSE) Recombination can occur with a virus that has a non-segmented genome.
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false
(TRUE/FALSE) Reassortment can occur with a virus that has a non-segmented genome.
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larger
DNA viruses are generally (LARGER/SMALLER) than RNA viruses.
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gene segment
Recombination occurs in a single ________ ________
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proteins
Enzymes and inhibitors are examples of viral ____________.
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enzymes
Retroviral integrase, reverse transcriptase, and nucleic acid polymerases are important viral _____________
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retroviral integrase
Enzyme produced by a retrovirus that enables it to integrate its genetic material into the DNA of the infected cell.
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reverse transcriptase
Enzyme used to generate complementary DNA from an RNA template.
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nucleic acid polymerase
Enzyme required for viral genome replication.
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viral nonstructural proteins
Proteins that play roles within the infected cell during virus replication or act in the regulation of virus replication or assembly. They are encoded by a viral genome and produced in the infected cell, but not packaged into the virus particles.
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false
(TRUE/VALSE) Nonstructural proteins are seen in extracellular virions.