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Exam 27: Viruses

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Question 21

Multiple Choice

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

A) binding to a host cell
B) leaving a macrophage
C) inserting its genes into the host cell's genome
D) assembling the capsid

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Question 22

Multiple Choice

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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) :

A) bacterium
B) archaean
C) fungus
D) virus

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Question 23

Multiple Choice

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

Viruses are ______ -coated fragments of DNA or RNA.

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

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?

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.

Viruses are characterized by all of the following except

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

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

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?

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?

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.

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

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

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

Nearly all viruses are constructed of

Virulent viruses multiply within infected cells and eventually

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?