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66 Cards in this Set

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Animal viruses have an _____ or _____ genome that is either double or single stranded.
DNA or RNA
Animal viruses are surrounded by a protein coat called a _______.
Capsid
The nucleic acid and the capsid are called __________.
Nucleocapsid
Some viruses have an ________ which acts as a phospholipid bilayer membrane that was obtained from the cell in which the virus arose.
Envelope
Viruses are _________ intracellular ___________.
Obligate intracellular parasites.
Viral genomes vary. Define:
Polioviruses
Herpeviruses
Retroviruses
Influenza viruses
Poliovirus = ss RNA
Herpevirus = ds DNA
Retrovirus = Diploid ss RNA
Influenza Virus = multiple gene segments of ss RNA
What is the simplist genome and largest genomes of animal viruses?
Hantavirus = simplist = 3 genes that encode 4 polypeptides
Pox virus = most complicated = 200 genes
What is the nomenclature rule for viruses?
Viruses are names for the geographic region in which they are discovered.
What are the three things that are used to classify viruses?
1. Genome structure
2. Virus particle structure
3. Presence or absence of an envelope
Viruses are grouped based on their __________ _________.
Transmission mechanism
What are the four groupings of transmission mechanisms?
1. Enteric viruses (fecal-oral route)
2. Respiratory viruses (aerosols)
3. Zoonotic agents (biting or resp. route)
4. Sexually-tranmitted
Viruses tend to be species and cell ________.
Specific
Step 1 of infection is called __________.
Attachement
Attachement is mediated by ____-_______ molecule(s) and viral ______ _______.
Cell-surface
spike proteins
HIV gp120 is specific for CD4, which are principally found on ________ ____ cells.
Helper T cells
Attachement occurs by _________ interactions.
Noncovalent
Some viruses ______ with a cell's plasma membrane. HIV's gp___ interacts with a cellular __________ receptor to induce fusion.
Fuse
gp41
chemokine
In both fusion and endocytosis, the ________, containing the nucleic acid and viral enzymes, is ________ into the _________.
Capsid
dumped
cytoplasm
Most DNA viruses replicate in the __________, while most RNA viruses replicate in the __________.
DNA = Nucleus
RNA = Cytoplasm
Some viruses ________ their dsDNA into the host cell's genome. Some viruses copy their RNA into ______, which is then integrated into the host cell's genome.
Integrate
dsDNA
Uncoating is caused by the dissociation of the _______ _______ from the ________ subunits that make up the capsid. This causes the capsid to ___________ and liberates the nucleic acid.
Nucleic Acids
Protein subunits
Disintegrate
Some RNA virus genomes act as a mRNA, these are termed:
plus-strand viruses
If a virus is not a plus-strand it has a prepackaged, _____-encoded ____-dependant RNA pol and is termed a ______-strand virus.
virus-encoded
RNA-dependant
Minus-strand
DNA viruses encode ____ polymerases.
RNA
Many viruses have ______cistronic mRNA's.
Polycistronic
Step 6 of infection is:
Maturation
Maturation of a virus in a cell involves the ________ of polycistronic polypeptides into ________.
Cleavage
Subunits
Nucleic acids and capsid proteins spontaneously __________ into ___________.
Polymerize
Nucleocapsid
HIV gp____ polypeoptide is cleaved into its gp____ and gp___ mature polypeptides. This step is inhibited by the ____ ________ __________ taken by HIV+ people.
gp160 --> gp120 and gp41
HIV protease inhibitors
Step 7 of infection is:
Release from cells
Some viruses rely upon _____ ______ for release into the extracellular matrix. This is like a balloon being blown up till it pops.
Cell lysis
Other viruses rely upon ________, whereby they exit from the cell, taking some of its membrane. These viruses don't exceed the capacity of the cell.
Budding
Budding occurs in one of three places depending on the viral species, these locations are:
The plasma membrane, the Golgi or the ER
Step 8 of viral infection is:
Shedding from the host
__________ ________ ________ would be an example of a catastrophic shedding event, while a ______ _____ is an example of a minor shedding event.
Hemorrhagic fever virus
Common cold virus
Step 9 of infection is:
Trasmission to other hosts
Transmission routes usually reflect the ______ of _________ for viruses.
Site of infection
List the 3 types of persistant infections:
1. Latent
2. Chronic
3. Slow
Hepatitis ___ is the greatest current health risk.
C
__________ ________ refers to even if you get vaccinated, if you're exposed heavily, you can still get the virus.
Vaccine breakthru
List the 3 mechanisms that account for viruses driving cell proliferation:
1. Oncogenes stimulate cell proliferation
2. Viral DNA integrates adjacent to genes that drive cell division
3. Some viruses encode growth factors
Epstein-Barr virus encodes the growth factor _______ __________-10 that causes ___ cell proliferation, leading to ________ ___________.
Viral interleukin-10
B cell
Burkitt's lymphoma
Influenze A viruses have ___ gene segments that encode 10 polypepetides. Segment __ and ___ are prominant in causing outbreaks
8
Segments 6 and 4
Latent infections
-Periods of inactivation and activation
-Usually limited pathology
-Herpes viruses
Chronic infections
Infectious virus can be detected for years or decades with little discernable pathology but can eventually lead to disease
-Hep B and C viruses
Slow infections
-Short period of acute infection followed by apparent disappearance of virus for months or years with pathology ensuing
-HIV
Tumor viruses drive cell ________ so they can have more homes.
proliferation
_________ viruses, like influenza, contain multiple genetic elements that encode different genes.
Segmented
________ of a cell with two or more different strains of a virus can lead to the emergence of __________ viruses that have distinct characteristics. This is called ___________.
Coinfection
Reassortant viruses
Reassortment
The H5N1 influenza virus has subtype __ ____ segment and subtype __ ____ segment.
5 HA
1 NA
What are the two main methods used to study viruses?
1. Cultivation of host cells
2. Cell culture
Cultivation of host cells involves __________ chicken eggs that must be _________ to the virus.
Embryonated
Suseptible
The two main targets in cultivation of host cells are:
1. Chorioallantoic fluid (CAF)
2. Embryo
Step 2 of infection is:
Entry into the cell
Other viruses are internalized by _________.
endocytosis
In both fusion and endocytosis, the ________, containing the nucleic acid and viral enzymes, is ________ into the _________.
Capsid
dumped
cytoplasm
Step 3 is:
Step 4 is:
Targeting to the site of replication
Uncoating
(these steps go together)
Most DNA viruses replicate in the __________, while most RNA viruses replicate in the __________.
DNA = Nucleus
RNA = Cytoplasm
Some viruses ________ their dsDNA into the host cell's genome. Some viruses copy their RNA into ______, which is then integrated into the host cell's genome.
Integrate
dsDNA
Uncoating is caused by the dissociation of the _______ _______ from the ________ subunits that make up the capsid. This causes the capsid to ___________ and liberates the nucleic acid.
Nucleic Acids
Protein subunits
Disintegrate
Step 5 of infection is:
Nucleic acid replication and protein synthesis
If a virus is not a plus-strand it has a prepackaged, _____-encoded ____-dependant RNA pol and is termed a ______-strand virus.
virus-encoded
RNA-dependant
Minus-strand
In a cell culture, cells are grown attached to flasks in a ________, inoculated with the virus and within days, ________(CPE) effect can be seen.
Monolayer
Cytopathic effect
Prions are...
Prions cause...
-Proteinaceous infectious particles
-spongiform encephalopathies
Prions contain no _______ acids. They are a normal cellular protein that has ________ into a ________ protein.
Nucleic
Misfolded
Pathogenic
List 3 diseases caused by prions;
1. Creutzfeldt-Jakob (from mad cows)
2. Kuru (religious consumption of brains of deceased)
3. Chronic wasting disease (deer, elk, moose)