MCM 2-17 DNA Viruses I Flashcards Preview

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Flashcards in MCM 2-17 DNA Viruses I Deck (29)
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DNA viruses (except poxvirus) use the host RNA Pol II enzyme to synthesize mRNA.
What else is needed for viral mRNA transcription?

A. Cellular DNA fragmentation induced by apoptosis.
B. High concentrations of capsid proteins.
C. RNA-dependent RNA polymerase on cell membranes.
D. Viral and cellular transcription factors that bind to viral gene promoters.
E. Viral or cellular DNA Polymerase and accessory proteins.

D - Viral and cellular TF that bind to viral gene promoters


Which are more genetically stable, DNA viruses or RNA viruses. Why?

DNA polymerases of both host and virus have higher fidelity than RNA polymerases


Genome replication of large DNA viruses occurs in the nucleus and
requires which of the following:
A. Cellular DNA fragmentation induced by apoptosis.
B. High concentrations of capsid proteins.
C. RNA-dependent RNA polymerase.
D. Viral and cellular transcription factors.
E. Viral DNA Polymerase and accessory proteins.

E - Viral DNA polymerase (because they are big like herpes and adenovirus) and accessory proteins


Adenovirus is associated with associated with which of the following diseases?
A. Gastroenteritis
C. Pharyngoconjunctival fever
D. Pneumonia
E. All of the above
F.None of the above

E - all


Treatments for adenovirus infections include these options:
A. Chemical ablation
B. Cidofovir
C. Cryotherapy
D. Infection control
E. Oncotherapy

B - cidovir


The initial phase of human papilloma
virus infection occurs in which cell type

basal epithelium


Treatments for human papilloma virus infection include these options:
A. Chemical ablation
B. Cryotherapy
C. Colposcopy
D. VLP vaccine
E. All of the above
F.None of the above

All of the above


The life cycle of adenovirus follows these steps:

1.Attachment – Adenovirus protein binds to cell receptor.
2. Entry – Occurs by endocytosis. Acidification of the endosome causes the lysis of the capsid’s fibers, which serve to break open the endosome.
3. Uncoating – The capsid traffics to the nucleus and the DNA genome uncoats through the nuclear pore. RNA gets made, exits cytoplasm, gets made into E1A as a transcription factor.
4. Transcription – Early on in the life cycle, the viral genes are transcribed into mRNA. As transcription factors are synthesized, transcription can occur at an even greater rate.
5. Replication – Viral DNA polymerase becomes available due to transcription, and DNA replication begins.
6. Capsid Assembly – Capsid protein genes are transcribed later on after the viral genome has been replicated many times.
7. Egression – Virions egress by lysis.


The key features of the DNA virus lifecycle are:

•Transcription and DNA replication occur in the nucleus (exception: poxvirus)
•Host RNA polymerase II transcribes viral mRNA (exception: poxvirus)
•Viral or host DNA polymerase replicates genome


The host RNA pol II as well as host and viral transcription factors recognize...

viral promoters. The availability or lack of the proper host transcription factors will affect a virus’s ability to function in the host. The viral transcription factors are also important; they are key virulence factors and are sometimes essential to a virus’s success.


some viral DNA sequences are recognized by...

DNA polymerase; such viruses do not encode their own DNA polymerase due to their smaller genome sizes, and they need host DNA polymerase to replicate their genome. Larger viruses encode their own DNA polymerases. Recombination does occur within and between genomes in DNA viruses; however, since DNA polymerases have higher fidelity than RDRP, DNA viruses are more genetically stable than RNA viruses.


adenoviruses are enveloped (TF)

F - they are unenveloped.


what can adenovirus infect?

various parts of the body. They can cause respiratory diseases ranging from a bad cold with a fever to laryngitis and pneumonia. They can also cause gastroenteritis, epidemic keratoconjunctivitis, and other diseases outside the respiratory system.


how is adenovirus passed?

aerosols, fecal-oral, contact with contaminated object/people.
Places where a lot of people are brought together and are in physical contact are common outbreak sites (e.g. daycare centers, swimming clubs, and military boot camps).


prevention/treatment of adenovirus

Adenovirus can be prevented with a vaccine, though it is used only for military personnel. Different tests for adenovirus are available depending on the patient sample obtained. Culture assays, antigen detection, PCR, and serological assays are all potentially usable. Currently, the only treatment is cidofovir, which is nephrotoxic and therefore reserved for dire cases.


HPV enveloped or non enveloped?

what diseases?


They can cause epithelial diseases (common, plantar, and genital warts) as well as a variety of cancers (head and neck, cervical, and penile cancers). Currently, HPV is the most commonly diagnosed STI in the US.


what vaccines exist for HPV>

Virus-like particle (VLP) vaccines exist for HPV: they are Gardasil and Cervarix. VLP’s are empty capsids. DNA tests are used to diagnose HPV. It is important to screen for the thirteen high-risk types linked to cancer. Warts can be treated by cryotherapy (freezing), chemical ablation, or excision. Cancers are treated with oncotherapy.


describe HPV sheddin

HPV will infect precursor skin cells, and then the virus will exist as a molecule of circular DNA in an episome.

The episomal HPV DNA is replicated within an individual cell sparingly, but during each cell division, the host DNA polymerase replicates the HPV DNA along with its own and distributes it between the daughter cells.

The virus remains dormant as the cell line divides and differentiates, and it becomes active in the permissive, fully differentiated cells; it is sensitive to the environment at the top layer of the skin where the differentiated epithelial cells are located.

As infected cells approach the surface of the top layer, they replicate the virus; once they arrive at the surface, the virion is shed.

If the immune system fails to clear the virus out, it can persist in the cells for years. These cells will continue to express early life cycle genes, leading to an invasive carcinoma.


Transcription of DNA virus mRNA is done by..

Host RNA polymerase


Replication of the DNA virus genome is accomplished by ..

host or viral DNA polymerase


____ are necessary for viral mRNA transcription. This can make a cell _____ or not.

host or viral transcription factors

permissive (does the cell have the right TF to bind the viral DNA?)


DNA Viruese use _______ RNA Pol for trancription of mRNA

host rna pol


X and Y?

X and Y are proteins that enhance viral transcription, can be viral or host proteins. can be multiplicative or synergistic


Some viruses genomes are recognized by the host dna Pol complex. implications?

DNA pol is around during S phase. Viruses that use host DNA pol complex must wait until cell divides nad they can only infect cells that divide.


which virus packages its own DNA pol, ready to go, on its ___ end.

adenovirus packages its own DNA polymerase at the 3' end, ready to go.

Herpes has the gene for its own DNA pol, but it is not pre-assembled and attatched.


which type of viruses have greater mutation rate? how do each type get diversity?

RNA has higher mutation rate, gets diversity through the RNA pol mistakes (no proofreading). more point mutations

DNA has lower mutation rate due to proofreading of DNA polymerase. diversity comes from recombination.


gene expression phases

Immediate - RNA (E1A)
Early - Pol, DBP, Pre-TP
Late - structural capsid proteins


Viral Factors E6 and E7 are



Host RNA Pol _______
Host DNA pol ________
Viral factors e6 and e7 are ____

transcribes viral mRNA
sythesizes viral genomes
are oncogones

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