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Exam 27: Viruses

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Question 21

True/False

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The pneumonia caused by the influenza virus results from the accumulation of fluid and cell debris in the lungs.This occurs during the lysogenic life cycle of the virus.

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Question 22

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Vibrio cholerae lives in water and gets toxin genes from a virus by phage conversion.The toxin kills the intestinal epithelial cells in the human host, resulting in massive diarrhea.Untreated cholera has about a 50% mortality rate.How do the bacteria benefit?

A) Diarrhea helps the bacteria to spread from person to person.
B) Killing humans provides nutrients for the bacteria.
C) They don't -- humans are not the main host and their symptoms are maladaptive for the bacteria.
D) The bacteria reproduce faster in a dead human.

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Question 23

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HIV infects cells by recognizing the cell-surface markers with its own

Viruses may cause cancer in these three typical ways: __X__ Some viruses encode an oncogene in their genome.__X__ A viral genome may integrate into the host chromosome, disrupting a cell cycle gene.__X__ Some viral proteins interact with cell cycle regulatory proteins._____ Viral infection provides large amounts of nutrients, encouraging the cell to divide and proliferate._____ All viruses promote host cell proliferation, as a way to spread more virus._____ Cell proliferation is an adaptive response of the host to any viral infection, to outgrow the virus._____ When a DNAvirus brings extra DNA into the host cell, that signals that S phase is complete.

Virulent viruses multiply within infected cells and eventually

Viruses are characterized by all of the following except

The direction of genetic information transfer in a retrovirus (such as HIV) is

If a virus enters the lytic phase in a host's cell, it will cause the host cell to

An experimental chemical has been shown to selectively cleave phosphodiester bonds.How would this affect a virus?

_____________ infects the CD4+ T cells, which are required for normal immunity.

If the gp120 glycoprotein were damaged as a result of a mutation, HIV would have difficulty:

Plasma from a sick mouse is filtered across a membrane that has a 200 nm pore size.If the filtrate is still infectious when injected into a healthy mouse, then the pathogen is most likely a(n) :

Retroviruses are unique because they are a combination of RNA and DNA.

While they are simple relative to cells, viruses often have a very diverse collection of components.Which one of the following choices is LEAST likely to be found as part of a virus?

The enormous genetic diversity of HIV has made it especially difficult to create a vaccine against the virus.We can attribute this genetic diversity to

Nearly all viruses are constructed of

Viruses are ______ -coated fragments of DNA or RNA.

Viruses that become established as stable parts of the host cell genome are called

Once a prophage is present in a bacterial genome, viral genes are reproduced every time the bacterium multiplies.Expression of viral genes, however, is inhibited by a repressor protein.Cell stress can induce the formation of proteases that degrade the repressor.What will result?

Which of the following is a virus with an icosahedral head, a capsid that contains primarily three proteins, a connecting neck with a collar and long whiskers, a long tail and a complex base plate?