Deck 12: Viruses

Question 1

Examine the figure shown.Which viral classification group must package a viral RNA-dependent RNA polymerase?

A) Group V
B) Group IV
C) Group III
D) Group II

Answer 1

A

Question 2

If 100% of the DNA contents of a transducing bacteriophage were DNA from the host chromosome,what would happen when the bacteriophage infected a new bacterial cell?

A) More bacteriophage would be synthesized, resulting in death of the new bacterial cell.
B) No more bacteriophage would be synthesized, as there is no bacteriophage genome available to direct synthesis.
C) The new bacterial cell would die.
D) The bacteriophage would be converted from a lysogenic phage to a lytic bacteriophage.

Answer 2

B

Question 3

Which of the following could possibly be an ancestor of the large asymmetrical DNA Vaccinia virus?

A) a degenerate single-celled organism
B) a bacteriophage
C) influenza
D) a cow

Answer 3

A

Question 4

Which of the following is NOT a level of viral evolution?

A) within an organelle
B) within a host community
C) within a viral species population
D) within an individual organism

Question 5

One positive use of viruses is their function as

A) infectious particles.
B) pandemic initiators.
C) cloning vectors.
D) marine predators.

Question 6

Replication of HPV is activated when

A) the DNA is uncoated.
B) infecting basal cells.
C) integrating into the host genome.
D) keratinocytes differentiate.

Question 7

Which of the following facts supports the argument that viruses are living?

A) Viruses lack metabolism for energy and biosynthesis.
B) Viruses are capable of being crystallized.
C) Some living pathogenic bacteria contain degenerate genomes and rely significantly on a host.
D) Viruses cannot replicate without a host.

Question 8

How is HPV able to keep its genome so small?

A) overlapping reading frames
B) oncogenic transformation
C) antigenic shift
D) HPV does not have a small genome.

Question 9

Examine the figure shown.What is indicated by the lines?

A) plaques
B) bacterial cells
C) latent virus
D) animal virus

Question 10

Which of the following is NOT a possible effect of viral replication in the host cell?

A) death of the cell
B) differentiation of the cell
C) debilitation of the cell
D) alteration of the genome of the cell

Question 11

Why must the genome of HPV enter the nucleus for replication?

A) HPV uses its own polymerase that cannot function in the cytoplasm.
B) The pH of the nucleus allows for replication of HPV RNA.
C) The DNA genome of HPV can only be replicated in the nucleus where host DNA polymerase is found.
D) The genome of HPV is not replicated in the nucleus.

Question 12

Examine the figure shown.Which viral classification group would be most NEGATIVELY affected by antiviral reverse transcriptase inhibitors?

A) Group III
B) Group IV
C) Group V
D) Group VI

Question 13

West Nile virus is capable of infecting many different organisms (humans,birds,raccoons,and so on).Based on this information,which of the following statements correctly describes West Nile virus?

A) West Nile virus has a narrow host range.
B) West Nile virus has a broad host range.
C) West Nile virus has a narrow tissue tropism.
D) West Nile virus is capable of fecal-oral transmission.

Question 14

________ bacteriophage infection results in immediate death of the host cell.

A) Lysogenic
B) Lytic
C) Latent
D) Chronic

Question 15

Which of the following is NOT caused by an aberrant protein?

A) Creutzfeldt-Jakob disease
B) scrapie
C) hepatitis
D) kuru

Question 16

Why is gelatin needed to culture animal viruses in tissue culture?

A) Animal viruses use gelatin as an energy source.
B) Cells in tissue culture require gelatin to grow.
C) Gelatin slows the dispersal of viruses from infected cells, allowing for plaques to form.
D) Gelatin is used to stain viral plaques.

Question 17

________ is an example of a virus that causes major economic losses in the agriculture industry.

A) Tobacco mosaic virus
B) Measles virus
C) HIV
D) Influenza

Question 18

________ ensures the presence and expression of host surface proteins capable of being bound to by viruses.

A) Transduction
B) Natural selection
C) Lysogeny
D) Lysis

Question 19

What type of HPV causes cancer?

A) all types of HPV
B) no types of HPV
C) some types of latent HPV
D) all types of actively replicating HPV

Question 20

Which of the following characteristics of the rabies virus is most important for its classification?

A) complex capsid morphology
B) single-stranded, negative sense RNA genome
C) presence of an envelope
D) narrow host range

Question 21

Why must influenza have highly efficient host-to-host transmission?

A) because of its rapid infection
B) because of its slow infection
C) because of genetic reassortment
D) because of latent infection

Question 22

A phage genome integrated into the DNA of the bacterial host cell is known as a ________.

Question 23

Segmented influenza RNA genomes are capable of

A) reverse transcription.
B) cell fusion.
C) reassortment.
D) proviral transposition.

Question 24

Why would a virus have evolved to cause cancer in a host cell?

A) to kill the host cell
B) to produce more cells for the virus to infect
C) to allow for increased mutagenesis of the virus
D) Viruses are not capable of causing cancer in a host cell.

Question 25

CASE HISTORY
Sean was a 19-year-old college sophomore,a member of a fraternity at a large Midwestern university.Sean visited the campus health center,where he told the nurse practitioner that the shaft of his penis had a raised spot.The spot caused no discomfort yet,but Sean knew it was abnormal.The practitioner told Sean that he probably had human papillomavirus (HPV),a cause of genital warts.Although some HPV strains cause warts on external skin,genital HPV is transmitted only by sexual intercourse.The practitioner conducted a physical exam and discovered additional raised spots on Sean's anus.Sean told the practitioner that he had recently had vaginal sex with women,and had also experimented sexually with other men.The practitioner told Sean that the warts would probably go away on their own if he maintained good sleep and health habits,keeping his immune system strong,but some HPV strains can persist for years without symptoms.The warts could be removed by freezing or chemical treatment,but the virus would persist.Meanwhile,the presence of HPV suggested that Sean was likely to contract related strains causing cancer of the penis or anus.The practitioner recommended use of condoms,although HPV may infect areas that condoms do not protect.She also suggested that Sean recommend the Gardasil HPV vaccine for his younger brother and sister before they become sexually active.
Which of the following is true of papillomavirus infection?

A) Genital HPV can be contracted via contact with warts on another person's skin, for example a wart on the fingers.
B) Condoms provide full protection against genital HPV.
C) Freezing or otherwise removing genital warts eliminates the infection.
D) The HPV vaccine can prevent infection with cancer-causing HPV strains.

Question 26

An infectious particle with an RNA genome and no capsid is known as a ________.

Question 27

What happens to the host cell after budding of new influenza virions?

A) It becomes cancerous.
B) It becomes transformed.
C) Nothing happens.
D) It is destroyed.

Question 28

________ proteins are expressed during viral infection of a host cell and are packaged between the envelope and the capsid during envelope formation.

Question 29

Where are HPV virions assembled?

A) in the nucleus
B) in the cytoplasm
C) in the ribosome
D) outside the cell

Question 30

Human papillomavirus contains a ________ genome.

Question 31

Which of the following characteristics do HPV and HIV have in common?

A) They are both retroviruses.
B) They both have overlapping genes.
C) They are both DNA viruses.
D) The have the same tissue tropism.

Question 32

What is the cure for infection with HIV?

A) vaccine
B) radiation
C) antiviral drugs
D) There is no cure for HIV.

Question 33

Which of the following statements regarding the influenza virus is FALSE?

A) The genome of influenza is very tiny to allow the generation of as many virions as possible.
B) The influenza genome maximizes gene reassortment.
C) The genome of influenza is well designed for evasion of the immune system.
D) The influenza genome allows for large quantities of virions to be created for continued infection.

Question 34

Which of the following viruses is capable of causing a syncytium?

A) hepatitis
B) influenza
C) HPV
D) HIV

Question 35

Which of the following features of HIV is a big reason as to why thus far it cannot be cured?

A) It is a retrovirus.
B) It contains a viral envelope.
C) It contains integrase.
D) It contains a protease.

Question 36

A small subset of the human population does not express the CD4 and CCR5 receptors.To what virus are these individuals naturally immune?

A) HIV
B) HPV
C) influenza
D) hepatitis

Question 37

Which of the following stages of the influenza infection cycle is inhibited by Tamiflu?

A) the coating of the capsid envelope
B) the assembly of the capsid
C) the cleaving of the host receptor and release of the virus by budding
D) the packaging of viral genome segments and exit from the nucleus

Question 38

________ is an example of a virus with a large double-stranded DNA viral genome.

Question 39

Why are so few HIV virions released in the blood actually infectious?

A) Reverse transcriptase has a high error rate.
B) HIV is not a very infectious virus.
C) The immune system inhibits these virions from causing infections.
D) Very few cells in the immune system express the receptor HIV requires for binding.

Question 40

What type of HPV can be eliminated from the body by the host immune system?

A) oncogenic HPV
B) nononcogenic HPV
C) all HPV
D) no HPV

Question 41

Why have the majority of viruses evolved to bind to a host surface receptor that serves an essential function in the host cell?

Question 42

Differentiate between antigenic drift and antigenic shift.Explain how one can lead to a global pandemic.

Question 43

CASE HISTORY
Eighteen-year-old Aisha was a first-year student at a small private college in New England.In the fall of 2009,the campus implemented management procedures for the expected H₁N1 influenza pandemic.Students with flu symptoms were told to "self-isolate" and to report their status on a college webform.By the end of October,there were 50 students reporting per week.
One night,Aisha felt hot,flushed,and unsteady on her feet.Her thermometer showed a temperature of 39°C (102°F).She started coughing,and she felt extremely tired.She managed to find the webform on her computer,although her arm was shaking and made false starts.Finally,she typed her information and confirmed her status report.A college security officer arrived at her room wearing a face mask.The officer gave Aisha a face mask and told her to collect her essential personal items and books;Aisha did the best she could in her fevered state.The officer drove her to a separate residence reserved for suspected H₁N1 cases.There Aisha lay in the bed and tried to sleep.In the morning a nurse's aide brought a tray of food and medication including oral oseltamivir (Tamiflu)and inhaled zanamivir (relenza).The tray was left on the floor in the hallway,outside Aisha's isolation room.Aisha had to drag herself out of bed to open the door and get the tray.She was required to stay in the isolation room until two days after her temperature returned to normal.She and most other infected students made a full recovery,although one student was hospitalized with life-threatening complications.
The college security officer who interacted with Aisha when she contracted H₁N1 influenza had received a flu shot earlier in the season,before this strain was included in the vaccine.He had also previously been infected with influenza as a child.Why did this officer exercise such precaution (e.g. ,wearing a face mask)in interacting with Aisha? How is the influenza virus able to infect a person with previous immunity?

Question 44

Explain how antigenic drift requires individuals to get a flu vaccine yearly.

Question 45

Influenza contains a ________ genome.

Question 46

You are attempting to propagate bacteriophage of Bacillus cereus using a liquid batch culture.A growing culture of B.cereus is inoculated with your bacteriophage.Immediately after inoculation,you take a sample but are unable to detect any bacteriophage.What is happening?

Question 47

CASE HISTORY
At 24 years of age,Ralph had just been promoted at the car dealership where he worked in sales.He was ready to propose to his girlfriend,a bank clerk.It was several years since Ralph had engaged in risky behaviors,but he and his girlfriend both decided to get tested for STDs.That is how Ralph learned that he was HIV positive.The diagnosis came as a surprise,since Ralph had no symptoms of disease.His T-cell count,however,had dipped to 500 cells/mm3 (normal level is about 1,200 cells/mm3).Now he faced the dilemma of how to avoid infecting his future wife and how to conceive healthy children.
The doctor informed Ralph of his treatment options.The current recommendation of the Centers for Disease Control and Prevention (CDC)is to commence antiretroviral therapy as soon as an individual tests positive for the virus.A single daily pill was prescribed,containing tenofovir and emtricitabine (reverse transcriptase inhibitors,together marketed as Truvada).The advantage of early treatment with Truvada is the early halt in decline of T cells and the decrease in transmission risk.Some physicians,however,recommend starting antivirals only when T-cell counts fall below 500 cells/mm3,to delay the deleterious side effects of the drugs and to postpone selection for drug-resistant strains.Ralph was also told of options for conceiving children without infection,such as the "sperm washing" procedure that eliminates HIV from sperm for artificial insemination.He had a lot to discuss with his girlfriend.
Infection with lentiviruses such as HIV can be lethal;however,lentiviruses may potentially be used to save lives.What features of these viruses allow them to be used for gene therapy,and can they be used to fight disease? Be specific and include an example of a disease in which this approach could be employed.

Question 48

Lentiviruses like HIV can be used positively for ________.

Question 49

Imagine that a new form of gene therapy that can eliminate expression of heparan sulfate proteoglycans has been invented.Explain how this therapy would have both a positive result and a negative result.

Question 50

Examine the figure shown.If a chemical that inhibits the fusion of endosomes and lysosomes were added to influenza grown in cell culture,what effect would this have?

Question 51

A retrovirus that causes infections progressing slowly over many years is a ________.

Question 52

A herpes virus contains an icosahedral capsid that allows for radial symmetry.Explain why this type of capsid formation is beneficial for the virus.

Question 53

Explain why the HIV virion structure contains a tRNA from the host.