Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
164 Cards in this Set
- Front
- Back
|
poison
|
Virus means ___________ in latin.
|
|
|
infectious
|
A virus is an _________ particle
|
|
|
Virion
|
One virus particle is a _____________
|
|
|
1. very small
2. contain very few genes 3. nucleic acids can be either DNA or RNA 4. Only grow within living cells |
Name 4 viral features which distinguish them from cells.
|
|
|
20nm-300nm
|
How small are viruses?
|
|
|
4-200 genes
|
How many genes does a virus have?
|
|
|
1. ssDNA
2. dsDNA 3. ssRNA 4. dsRNA |
What are the 4 types of nucleic acid types found in viruses?
|
|
|
obligate intracellular parasites
|
A virus only grows within living cells so they are _______.
|
|
|
host cell
|
Viral proteins manufactured and nucleic acids replicated by the _______.
|
|
|
False
|
Viruses have ribosomes. (true/false)
|
|
|
1. Make protein coat
2. Assure replication of own chromosome 3. Move in and out of cell |
What is the minimum genetic information in a virus?
|
|
|
1. Polyhedral
2. Helical 3. Complex |
What are the three shapes of viruses?
|
|
|
Polyhedral
|
a virus having many flat surfaces
|
|
|
Helical
|
A viral shape in which capsomeres are spiraled around a core.
|
|
|
Complex
|
a combination of both helical and polyhedral shape.
|
|
|
the shape of its protein coat (capsid)
|
What determines the shape of the virus?
|
|
|
Envelope
|
What is the membrane that surrounds the capsid of some viruses?
|
|
|
Host cell plasma membrane
|
Where does the virus acquire an envelope?
|
|
|
Budding
|
What method of exit from the host cell results in an envelope?
|
|
|
1. In the nucleus
2. the cytoplasm of the host cell |
Where do animal viruses replicate?
|
|
|
adsorption
|
The first step in infection is ______of the virus to the host cell.
|
|
|
specific host cell receptors
|
Where do viruses attach in the host?
|
|
|
receptors
|
The host cell is resistant if it lacks ________ to the virus.
|
|
|
1. fusion
2. endocytosis |
What are the two methods of viral entry?
|
|
|
envelopes
|
Fusion occurs between the cytoplasmic membrane of the host with the virion ___________.
|
|
|
endocytosis
|
Both naked and enveloped virions enter by ________
|
|
|
Uncoating
|
The separation of the viral nucleic acid and the capsid is called ________.
|
|
|
replication
|
More viral nucleic acid is made by __________
|
|
|
synthesis
|
Capsid proteins are made by ___________.
|
|
|
Maturation
|
Self-assembly of viral component parts.
|
|
|
1. Lysis of dead cells
2. Budding from living cells. |
What are the two methods of viral release from a host cell?
|
|
|
1. dsDNA integrates into the host cell genome
2. dsDNA can replicate in host as a plasmid |
How does a dsDNA virus become part of the host cell genome?
|
|
|
Temin, Baltimore and
|
The scientists that discovered reverse transcriptase.
|
|
|
Host cell makes a DNA copy of the viral RNA using reverse transcriptase which is then integrated into the chromosome of the host cell.
|
How do RNA retroviruses become part of the host cell genome?
|
|
|
reverse transcriptase
|
What is the enzyme encoded by retroviruses that allows for the conversion of RNA to DNA?
|
|
|
Defence mechanisms
|
In the case of animals, outcome of infection depends on many factors independent of the infected cell such as the ______ of the host.
|
|
|
Balanced pathogenicity
|
The infection of an animal in which the microbe causes no obvious harm or disease.
|
|
|
Prions
|
Proteinaceous infectious particles
|
|
|
transmissible spongiform encephalopathies
|
Prions cause _____________
|
|
|
Viriod
|
Plant pathogens that are small ssRNA but no protein
|
|
|
May be escaped introns
|
Possible source of viriods.
|
|
|
Complex Virus
|
Virus morphology?
|
|
|
Polyhedral (icosahedral) virus
|
Virus morphology?
|
|
|
Helical Virus
|
Virus morphology?
|
|
|
Scrapie
|
Prion disesase seen in sheep and goats
|
|
|
Kuru
|
Prion disease seen in cannibals in New Guinea
|
|
|
Bovine spongiform encephalopathy
|
Mad cow disease
|
|
|
1. Creutzfeldt-Jacob disease
2. Kuru 3. Gerstmann-Straussler syndrome 4. fatal familial insomnia 5. Variant CJD |
Name the prion diseases of humans
|
|
|
PrPC
|
The cellular prion protein
|
|
|
PrPSc
|
Scrapie protein
|
|
|
Chronic Wasting Disease
|
What is the prion disease of deer and elk?
|
|
|
Kuru
|
Which prion disease is also known as laughing disease?
|
|
|
Transmissible mink encephalopathy
|
What is the prion disease of Mink?
|
|
|
Virus
|
_____ is a genetic element that cannot replicate independently of a living (host) cell
|
|
|
Virology
|
____ is the study of viruses
|
|
|
Viral infection
|
A _______ occurs when a virus enters a host cell
|
|
|
Conferring important properties.
|
Not all viruses damage host cells. They may even be beneficial to the host by ______
|
|
|
1.Either DNA or RNA genomes
2.Some circular, but most linear 3.single-stranded or double-stranded 4. one chromosome or segmented |
Describe viral genomes.
|
|
|
bacteriophages
|
Bacterial viruses are called ___________
|
|
|
viridae
|
Viral family names end in __________
|
|
|
smaller
|
Most viruses are ____ (smaller/larger) than prokaryotic cells
|
|
|
smaller
|
Most viral genomes ____ (smaller/larger) than those of cells
|
|
|
Capsid
|
________ is the protein shell that surrounds the genome of a virus particle
|
|
|
Capsomere
|
_____ is a subunit of the capsid
|
|
|
Nucleocapsid
|
________ is a complete complex of nucleic acid and protein packaged in the virion
|
|
|
Helical
|
Rod-shaped viruses have _______ symmetry
|
|
|
length of nucleic acid
|
Length of virus determined by________
|
|
|
size and packaging of protein subunits
|
Width of virus determined by _________
|
|
|
Icosahedral
|
Spherical viruses have ______ symmetry
|
|
|
20
|
Icosahedral viruses have _____ triangular faces
|
|
|
Complex Viruses
|
Virions composed of several parts, each with separate shapes and symmetries are _________
|
|
|
Icosahedral heads and helical tails
|
Describe a typical bacterial virus
|
|
|
Enveloped
|
A ____ virus contains additional membrane layers around the nucleocapsid
|
|
|
embedded proteins
|
The viral envelope is a lipid bilayer with______
|
|
|
Enzymes for entry into host cell
Enzymes that are used to replicate genome Enzymes to aid in release from the host cell |
What are the three types of enzymes critical to infection?
|
|
|
Neuraminidase
|
Enzymes that cleave glycosidic bonds
|
|
|
Lysozyme
|
Enzyme that makes hole in cell wall of bacteria
|
|
|
Bacterial
|
___ viruses are easiest to grow and are used as model systems
|
|
|
Plant
|
_____ viruses are typically most difficult to grow because study often requires growth of whole host
|
|
|
Titer
|
___ is the number of infectious units per volume of fluid
|
|
|
Plaque assay
|
____ are analogous to the counting bacterial colonies; one way to measure virus infectivity
|
|
|
Plaques
|
___ are clear zones that develop on lawns of host cells
|
|
|
Lawn
|
___ is a continuous (confluent) growth of bacterial or tissue culture
|
|
|
a single virus particle
|
Each plaque results from infection by _____
|
|
|
Plaque-forming unit (PFU)
|
____ is a measure of the number of virus particles capable of forming plaques per unit volume
|
|
|
Infectious unit (IFU)
|
____ is the smallest unit of virus that causes a detectable effect on a susceptible host
|
|
|
Viral particles (VP)
|
____ is the total number of viral particles, live and dead combined.
|
|
|
lower
|
The number of plaque-forming units is almost always ____ (lower/higher) than direct counts by electron microscopy
|
|
|
Inactive virions
Incomplete virions Conditions not appropriate for infectivity |
Why are plague-forming units lower than direct counts
|
|
|
ID50
|
The number of microbes to cause infection in 50% of test subjects.
|
|
|
LD50
|
The number of microbes to cause death in 50% of test subjects.
|
|
|
1 Attachment
2 Penetration 3 Synthesis 4 Assembly 5 Release |
What are the phases of viral replication?
|
|
|
Attachment
|
____ is adsorption of the virus to a susceptible host cell
|
|
|
Penetration
|
______ is entry of the virion or its nucleic acid
|
|
|
Synthesis
|
_____ is the manufacturing of virus nucleic acid and protein by cell metabolism as redirected by virus
|
|
|
Assembly
|
____ is maturation of capsids and packaging of viral genomes into new virions
|
|
|
Budding
lysis |
____ and ____ are the two methods of release of mature virions from the cell
|
|
|
Endocytosis and fusion
|
The two methods of entry of animal viruses into a host cell.
|
|
|
Latent
|
eclipse + maturation is the _____ period
|
|
|
Enveloped
|
Only _______ viruses can enter an animal cell by fusion.
|
|
|
Eclipse
|
____ is the period between adsorption of virus and the appearance of assembled virus progeny inside the cell
|
|
|
Burst size
|
______ is the number of virions released
|
|
|
Class I
|
Class ____ are double-stranded (ds) DNA viruses
|
|
|
Class II
|
Class ____ are single-stranded (ss) DNA viruses
|
|
|
Class III
|
Class ____ are dsRNA
|
|
|
Class IV
|
Class ____ are ssRNA +
|
|
|
Class V
|
Class ____ are ssRNA -
|
|
|
Class VI
reverse transcriptase |
Class ____ ssRNA + retroviruses. Use _______ enzyme
|
|
|
Class VII
reverse transcriptase |
Class ____ are dsDNA viruses that replicate through an RNA intermediate using _______ enzyme
|
|
|
Attachment
|
_____ requires complementary receptors on the surface of a susceptible host and its infecting virus
|
|
|
carry out normal functions for cell (e.g., uptake proteins, cell to cell interaction)
|
Receptors on host cell that the virus attaches to is used by the host to ________.
|
|
|
penetration
|
The attachment of a virus to its host cell results in changes to both virus and cell surface that facilitate ____.
|
|
|
endocytosis
|
Naked and enveloped viruses can enter by ____
|
|
|
fusion
|
Only enveloped viruses may enter by ______
|
|
|
Uncoating
|
___ is the process in which virions lose their outer coat and exposes the genome.
|
|
|
Permissive cell
|
____ is a host cell that allows the complete replication cycle of a virus to occur
|
|
|
bacteriophage
|
The type of virus that attaches to cells via tail fibers that interact with polysaccharides on the outer membrane of the host cell is a ____
|
|
|
immune defense mechanisms
RNA interference |
What are the eukaryotes mechanisms to diminish viral infections?
|
|
|
CRISPR- Similar to RNA interference Restriction modification system
|
What are the prokaryotes mechanisms to diminish viral infections?
|
|
|
double-stranded DNA
|
DNA destruction system of bacteria are only effective against _____viruses
|
|
|
Restriction enzymes (restriction endonucleases)
|
____ cleave DNA at specific sequences
|
|
|
Chemical modification of viral DNA (glycosylation or methylation)
Production of proteins that inhibit host cell restriction system |
How does a virus evade bacterial restriction systems?
|
|
|
Baltimore
|
____developed classification scheme for viruses based on relationship of viral genome to its mRNA
|
|
|
retroviruses
reverse transcriptase |
Baltimore, Temin, and Dulbecco discovered ____ and _____
|
|
|
plus (+)
|
mRNA is said to be in ____ configuration
|
|
|
genome
proteins |
Once a host has been infected, new copies of the viral _____ must be made and virus-specific ____ synthesized in order for the virus to replicate
|
|
|
Positive
|
____strand RNA virus: single-stranded RNA genome with same orientation as its mRNA
|
|
|
Negative
|
____ strand RNA virus: single-stranded RNA genome with orientation complementary to its mRNA
|
|
|
1 synthesized soon after infection
2 necessary for replication of virus nucleic acid 3 typically act catalytically 4 synthesized in smaller amounts |
What are the characteristics of early proteins?
|
|
|
1 Synthesized later Include proteins of virus coat
2 Typically structural components 3 Synthesized in larger amounts |
What are the characteristics of late proteins?
|
|
|
dsDNA
|
Most phages contain ____ genomes
|
|
|
lytic
|
Temperate phages can also be ____
|
|
|
Early and middle proteins
|
____ are enzymes needed for replication and transcription
|
|
|
Late proteins
|
_____ are head and tail proteins and enzymes required to liberate mature phage particles
|
|
|
Lysogenic
|
Temperate viruses can undergo a stable genetic relationship within the host. This is the _____ pathway
|
|
|
Lysogeny
|
____ is a state where most virus genes are not expressed and virus genome (prophage) is replicated in synchrony with host chromosome
|
|
|
Lysogen
|
___ is a bacterium containing a prophage
|
|
|
lytic
|
Viruses can enter a virulent mode in which it kills cells through____ pathway
|
|
|
lytic
|
Under certain conditions lysogenic viruses may revert to the ____ pathway and begin to produce virions
|
|
|
Budding
|
____ occurs as animal viruses leave host cell, they can remove part of host cell’s lipid bilayer for their envelope.
|
|
|
Persistent
|
During ____ infections, release of virions from host cell does not result in cell lysis
|
|
|
Latent
|
During ____ infections, there is a delay between infection by the virus and lytic events
|
|
|
Transformation
|
____ is the conversion of normal cell into tumor cell
|
|
|
Cell fusion
|
___ occurs when two or more cells become one cell with many nuclei
|
|
|
Retroviruses
|
____ are RNA viruses that replicate through a DNA intermediate
|
|
|
two identical ssRNA molecules of the plus (+) orientation
|
Retroviruses have a unique genome which consists of __________
|
|
|
1.Entrance into the cell
2.Removal of virion envelope at the membrane 3.Reverse transcription of one of the two RNA genomes 4.Integration of retroviral DNA into host genome 5.Transcription of retroviral DNA 6.Assembly and packaging of genomic RNA 7.Budding of enveloped virions; release from cell |
What is the process of replication of a retrovirus?
|
|
|
Defective
|
_____ viruses that are parasitic on other viruses
|
|
|
Defective
|
_____ viruses require other virus (helper virus) to provide some function
|
|
|
Satellite
|
_______ viruses are defective viruses for which no intact version exists; rely on unrelated viruses as helpers
|
|
|
Viroids
|
____ are infectious RNA molecules that lack a protein coat
|
|
|
plant
|
Viriods cause a number of important ____ diseases
|
|
|
Small, circular, ssRNA molecules
|
Describe the genome of viriods.
|
|
|
Prions
|
____ are infectious proteins whose extracellular form contains no nucleic acid
|
|
|
transmissible spongiform encephalopathies
|
Prions cause disease in animals called ______
|
|
|
PrnP
|
Host nerve cell contains gene ___ that encodes native form (PrPc) of prion protein that is found in healthy animals
|
|
|
PrPc
|
The native form of prion protein that is found in healthy animals is ______
|
|
|
PrPSc
|
_____results form prion misfolding and causes neurological symptoms of disease (e.g., resistance to proteases, insolubility, and aggregation)
|
|
|
1.Infectious prion disease
2.Sporadic prion disease 3.Inherited prion disease |
What are the three distinct mechanisms of prion diseases?
|
|
|
Infectious
|
During _____ prion disease, a pathogenic form of prion protein is transmitted between animals or humans
|
|
|
Sporadic
|
During _____prion disease, random misfolding of a normal, healthy prion protein in an uninfected individual
|
|
|
Inherited
|
During _____ prion disease, a mutation in prion gene yields a protein that changes more often into disease-causing form
|
|
|
Virulent
|
During the _____ mode, viruses lyse host cells after infection
|
|
|
Temperate
|
During the ______mode, viruses replicate their genomes in tandem with host genome and without killing host
|
