Deck 27: Viruses

Question 1

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.

Answer 1

A

Question 2

Viruses are ______ -coated fragments of DNA or RNA.

Answer 2

protein

Question 3

Nucleotide analogs are a class of drugs that are highly effective against many types of viruses.They work by halting the replication of viral genes.They are equally effective at stopping the spread of prion diseases.

Answer 3

False

Question 4

Tetracycline is effective against viruses because it disrupts the action of the viral ribosomes.

Question 5

A ____________ can contain DNA or RNA as its genetic material, but not both.

Question 6

A doctor's office has run out of the latest flu vaccine, but many patients are asking for it.One of the nurses finds some vials from last year's batch in a refrigerator.Should they be used?

A)Yes, because the preservatives and refrigeration ensure that the vaccine is still fresh.
B)No, because each year the technology to make a good vaccine improves.
C)No, because each year the vaccine is made against different subtypes of the flu virus.
D)Maybe - the vaccine should be mixed in a test tube with the virus to see if it still inactivates it.

Question 7

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

Question 8

Can a virus be killed?

A)Yes, destroying its genome kills it.
B)No, viruses are capable of self-assembly and cannot be permanently killed.
C)Yes, separating the genes from the capsid kills it.
D)No, viruses are non-living and cannot die.

Question 9

Which class of drugs would be effective against HIV but not against most other pathogenic viruses?

A)Nucleotide analogs that halt replication.
B)Receptor antagonists that block viral entry.
C)Non-nucleoside reverse transcriptase inhibitors that block reverse transcription.
D)Translation inhibitors that stop assembly of viral proteins.

Question 10

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.

Question 11

A mutation in the gene encoding the integrase enzyme renders the protein non-functional.How would this affect-the HIV infection cycle?

A)The gp120 glycoprotein would not be able to bind the CCR5 receptor.
B)Reverse transcription would not be possible.
C)The viral DNA would not be able to integrate the viral genome into a chromosome.
D)Cutting and assembling the capsid would be halted.

Question 12

What best describes whether a virus is likely to infect a particular cell?

A)Viruses infect the first cells they encounter.
B)If a host cell is weakened, viruses are likely to infect it.
C)A virus will only infect host cells with the correct surface receptors.
D)Viruses only attack epithelial cells, such as the cells lining the lungs.

Question 13

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

A)Fragment the genome
B)Digest the capsid
C)Dissociate the envelope
D)Alter the host binding site

Question 14

Viruses can ________ only after they have entered a host cell, and only by using the host's cellular machinery.

Question 15

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

Question 16

Integrase inhibitors work by:

A)Agglutinating the reverse transcriptase inhibitors
B)Degrading the viral envelope
C)Preventing the incorporation of the viral DNA into the genome
D)Blocking the final viral assembly

Question 17

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?

A)The virus will enter the lysogenic cycle.
B)The bacterium will reject the viral genes.
C)The virus will enter the lytic cycle.
D)The bacterial genome will be denatured.

Question 18

Gardasil is marketed as a cervical cancer vaccine, but it is actually a human papilloma virus (HPV) vaccine.Why is this done?

A)The virus multiplies more rapidly in cancerous cells.
B)Cancer cells are particularly susceptible to viral infection.
C)Genital warts is a sign of cancer.
D)HPV in the cervical epithelial cells may cause the cells to become cancerous.

Question 19

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

Question 20

Viruses are self-replicating but the replication is much faster in a host cell.

Question 21

Viruses are characterized by all of the following except

A)being found in every organism investigated so far.
B)being specific to the hosts they infect.
C)being capable of independent reproduction.
D)being acellular.

Question 22

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

Question 23

A layer of lipoprotein and glycoprotein that covers the outer surface of some viruses is the

A)capsid.
B)casing.
C)envelope.
D)membrane.

Question 24

All of the following are diseases caused by viruses except

A)strep throat.
B)AIDS.
C)polio.
D)small pox.

Question 25

HIV studies revealed that it is closely related to

A)smallpox virus.
B)ebola virus.
C)herpes virus.
D)a chimpanzee virus.

Question 26

The HIV virus is considered a(n) ______ virus, because after getting integrated into the host cell chromosomes, it does not begin replicating immediately.

A)phage
B)latent
C)transforming
D)benign

Question 27

Nearly all viruses are constructed of

A)DNA with a protein wrapping, called a capsid.
B)RNA with a protein wrapping, called a capsid.
C)either DNA or RNA with a protein wrapping, called a capsid.
D)either DNA or RNA, however many do not have the capsid.

Question 28

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

A)lethal.
B)potent.
C)temperate.
D)virulent.

Question 29

Recently a class of infectious proteins with no associated nucleic acid have been identified.They are referred to as

A)bacteriophages.
B)latent viruses.
C)viroids.
D)prions.

Question 30

The specific white blood cells that HIV attaches to are the ____________ cells.

A)CD4+
B)gp120 -T
C)CCR5-T
D)CXCR4-T

Question 31

Scientists have demonstrated that the cholera bacteria, Vibrio cholerae, can exist as a rather harmless form or, by phage conversion, can exist as a disease-causing, virulent form.This conversion is caused by

A)the phage entering the cholera bacterium genome and causing the bacterium's cell to lyse.
B)the phage introducing a gene into the bacterium's chromosome that codes for the cholera toxin that can cause death in humans.
C)the phage altering the cell wall of the cholera bacterium that produces a toxin that can cause death in humans.
D)the phage alters the host cell, which permits direct entry of the cholera bacterium into the host cell leading to death in humans.

Question 32

Virulent viruses multiply within infected cells and eventually

A)cause an alternation of generations in the host cell, releasing new viruses.
B)cause the transformation of the host cell, releasing new viruses.
C)cause lysis of the host cell, releasing new viruses.
D)cause the transduction of the host cell, releasing new viruses.

Question 33

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

A)DNA.
B)glycoproteins.
C)reverse transcriptase.
D)capsid protein.

Question 34

The infection cycle of HIV includes all of the following steps except

A)attachment.
B)entry.
C)replication.
D)immediately killing the host cell.

Question 35

Prions are

A)strands of nucleic acids encased in a protein coat.
B)viral nucleic acids integrated into the host chromosomes.
C)viral-infected cells.
D)infectious proteins with no associated nucleic acid.

Question 36

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?

A)influenza virus
B)measles virus
C)T4 bacteriophage
D)HIV

Question 37

A scientist is studying the lysogenic cycle of the lambda 1 phage of Escherichia coli.This means that she is investigating

A)the integration and stabilizing of the lambda 1 phase into a host cell's genome.
B)the integration of the bacteria's genome with the viral genome outside of the bacteria's cell wall.
C)the integration of the viral genome into the ribosomes present in the bacteria to direct protein synthesis for the capsid formation.
D)the integration and stabilizing of a virus into its capsid, which provides protection until conditions are better for reproduction.

Question 38

The onset of AIDS is often accompanied by

A)a steep drop in T cell numbers.
B)macrophage infection.
C)a positive HIV test.
D)lung infections and other opportunistic infections.

Question 39

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

A)reject the virus.
B)shrink because of the loss of cytoplasm that has been used in the synthesis of viral DNA.
C)lysis due to the action of enzymes
D)replicate itself at a higher than normal frequency.

Question 40

Most viruses form a capsid around their nucleic acid core.This capsid is composed of

A)proteins.
B)monosaccharides.
C)glycoproteins.
D)lipoproteins.

Question 41

All of the following are part of phage conversion except

A)injection of phage gene into host.
B)transcription and translation of phage gene.
C)induction of phage.
D)expression of phage gene by host.

Question 42

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

A)mutation hotspots in the hemagglutinin (H) molecule.
B)mutation hotspots in the CD4⁺ molecule.
C)the high error rate of reverse transcriptase.
D)the high sensitivity of the virus to UV radiation.

Question 43

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

A)DNA to mRNA to protein.
B)RNA to DNA to mRNA to protein.
C)DNA to protein.
D)RNA to mRNA to protein.

Question 44

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?

A)proteins with functional binding sites
B)membrane components
C)single-stranded DNA
D)ribosomes

Question 45

What is the name for parasitic viral DNA that has been integrated into the chromosome of its bacterial host?

A)prophage
B)prophase
C)viroid
D)virion

Question 46

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.

Question 47

Which of the following statements about TSEs (transmissible spongiform encephalopathies) is false?

A)TSEs include scrapie in sheep, mad cow disease, chronic wasting disease in deer and elk, and kuru and variant Creutzfeldt-Jakob disease in humans.
B)The incidence of Creutzfeldt-Jakob disease in humans increased after an outbreak of mad cow disease in England, suggesting that mad cow disease may be transmitted to humans.
C)Viroids are the likely cause of TSEs.
D)TSEs do not seem to be affected by treatments that would eliminate nucleic acid-based diseases.

Question 48

The switch from a lysogenic prophage to a lytic cycle is called

A)transformation.
B)induction.
C)latency.
D)phage conversion.

Question 49

Diseases such as scrapie in sheep, "mad cow" disease in cattle, and Creutzfeldt-Jakob disease in humans are known as

A)viroids.
B)viruses.
C)retroviruses.
D)TSEs (transmissible spongiform encephalopathies).

Question 50

Which of the following is a unique feature of viruses that separates them from bacteria?

A)They are generally smaller.
B)They are often highly toxic.
C)They lack proteins.
D)They have different nucleotides in their hereditary material.