Deck 7: Viruses and Other Acellular Life

Question 1

Which of the following descriptions about the characteristics of viruses is true?

A) They contain nucleic acids like DNA or RNA.
B) They include metabolic pathways for synthesizing proteins.
C) They are unable to evolve.
D) The have the ability to infect only a single host species.

Answer 1

They contain nucleic acids like DNA or RNA.

Question 2

Which of the following descriptions of a virus is correct?

A) All viruses have single-stranded DNA.
B) All viruses have double-stranded DNA.
C) All viruses have nucleic acids.
D) All viruses have single-stranded RNA.

Answer 2

All viruses have nucleic acids.

Question 3

Which of the following instruments is required to see viruses?

A) light microscope
B) magnifying glass
C) fluorescence microscope
D) electron microscope

Answer 3

electron microscope

Question 4

Viruses are generally not considered to be living organisms because they

A) are too small.
B) cannot evolve.
C) cannot replicate independently.
D) have no mechanism for self-propulsion.

Question 5

Which of the following statements correctly describe rhinovirus?

A) It affects multiple tissues including liver and brain.
B) It affects just the cells lining the upper respiratory tract.
C) It is the cause of measles and mumps.
D) It infects several species of mammals, but not humans.

Question 6

Why does vaccination protect us from viral infection?

A) because the vaccination allows the immune system to recognize the virus and destroy it
B) because the vaccine will stay in the bloodstream and destroy the virus as it enters
C) because the vaccine will stay inside of the body's cells and prevent the virus from replicating
D) because the vaccination generally boosted the body's immune system, thus protecting it from all foreign invaders

Question 7

With respect to viruses, what does the term 'host range' mean?

A) the geographical area within which a virus is active
B) the number of different host species that a virus can infect
C) the range of the virus's host species
D) the genetic distance between sister viruses

Question 8

Following viral infection, new viral genes will be produced using the host cell's

A) nucleic acid pools.
B) DNA molecules.
C) RNA molecules.
D) genome.

Question 9

Viral 'early genes' are genes that are involved in

A) release of the virus from the host cell.
B) the initial interaction of the virus with the host cell surface.
C) synthesizing the viral envelope.
D) taking control of the host cell's regulatory processes.

Question 10

Which of the following best describes the initial interaction between a virus and a host animal cell?

A) It is the result of a random collision, and any virus can adhere to any cell.
B) Proteins on the virus's surface recognize specific proteins on the host cell.
C) Viral DNA binds to specific proteins on the surface of the host cell.
D) Cilia on the host cell will attempt to repel incoming viruses.

Question 11

Many viruses are surrounded by a 'viral envelope,' which is made from

A) membrane phospholipids taken from the host cell.
B) membrane phospholipids synthesized by the virus.
C) protein taken from the host cell.
D) protein synthesized by the virus.

Question 12

Which of the following best describes the infection of a host cell by an adenovirus?

A) The membrane surrounding the adenovirus fuses with the host cell membrane.
B) A hypodermic needle-like structure on the adenovirus injects its DNA into the host cell.
C) The virus must enter a damaged cell in which the membrane has been compromised.
D) The virus must enter the host cell while the host cell is replicating.

Question 13

A bacteriophage typically cannot infect a human cell because

A) human cells do not have a circular genome, which this type of virus requires.
B) the human cell wall blocks the injection of the bacteriophage genetic material.
C) macrophages destroy bacteriophages before they are able to infect other cells.
D) human cells lack the cell surface proteins that bacteriophages must interact with.

Question 14

If a pathogenic illness is transmitted through the ingestion of food, we know that it

A) must be a prion.
B) must be a virus.
C) could be a prion or virus.
D) must be a dsDNA virus.

Question 15

Which of the following statements regarding the life cycle of a virus is correct?

A) A virus will only interact with a single species.
B) A virus may interact with vector species and host species.
C) A virus will always kill the cell that it infects.
D) A virus will always kill the host species.

Question 16

To eradicate a virus like West Nile virus, one would need to control the populations of its mosquito vectors. Why?

A) because the virus is spread from person to person by mosquitoes
B) because mosquitoes spread the virus from people to birds, and the birds then disperse the virus quite widely
C) because mosquitoes can transmit the virus from birds to people
D) because mosquito saliva makes the symptoms of the virus worse

Question 17

In hospitals, multi-drug resistant bacterial strains that are not destroyed by antibiotics are a major issue threatening human life. One strategy to treat these might be

A) use of a bacteriophage that can infect the drug resistant bacterial strain.
B) use of a virus that can infect the drug resistant bacterial strain.
C) use of a prion that can infect the drug resistant bacterial strain.
D) use of a viroid that can infect the drug resistant bacterial strain.

Question 18

With respect to bacteriophage lytic and lysogenic cycles, which of the following statements is correct?

A) The lytic cycle should provide the most new bacteriophages.
B) The lysogenic cycle should provide the most new bacteriophages.
C) The lysogenic cycle followed by the lytic cycle should provide the most new bacteriophages.
D) The lytic cycle and lysogenic cycle provide about the same number of new bacteriophages.

Question 19

In mammals, viruses are able to move about the body in the blood. Plants do not have blood or arteries or veins, so how do viruses move from cell to cell?

A) Each time a plant cell is lysed by the virus, its neighbours become infected.
B) They do not move about; only one plant cell is ever infected by a virus.
C) They move through the plasmodesmata.
D) They move along the surface of the plant.

Question 20

The protein syncytin is

A) essential for the development of the human heart during pregnancy.
B) essential for development of the placenta during pregnancy.
C) encoded by a human gene.
D) a prion protein.

Question 21

Some viruses, like human papilloma virus (HPV) can cause cancer. How does HPV do this?

A) by killing healthy cells and thus giving cancerous cells an advantage
B) by stimulating re-entry into the cell cycle in infected cells
C) by causing mutations in the host cell's genome
D) by conferring resistance to anti-cancer drugs

Question 22

Why do viruses often seem to emerge from nowhere to become major public health scares in Canada?

A) because viruses are constantly evolving and sometimes this process leads to them gaining access to a new species (e.g., humans)
B) because over time our immune systems are becoming less robust so we are becoming more susceptible to the same viruses
C) because we hear about them on the news, whereas in the past we may have remained unaware of them
D) because the majority of Canadians have stopped getting vaccinated against common viruses

Question 23

Animal cells and viruses are in an ongoing 'arms race' to prevent and facilitate infection, respectively. Of the following evolved changes to the host, which do you think would be most effective at limiting viral infection?

A) development of RNAases to digest RNA
B) development of better apoptotic cell death pathways so that an infected host cell eliminates itself quickly to limit viral replication
C) altered structure of the cell surface protein(s) that the virus recognizes to 'find' and bind to a prospective host cell
D) acquiring a mechanism to fully inhibit ribosome function to prevent proteins, including viral proteins, from being made

Question 24

The deadliest viruses for a population of people tend to be those which

A) that population has never come in contact with before.
B) have the most DNA or RNA.
C) infect the respiratory tract or the digestive system.
D) have been in existence for a very long time.

Question 25

The genetic reshuffling of DNA from multiple viruses to create new and sometimes deadly viruses is an example of

A) evolution involving horizontal gene transfer between viruses.
B) survival of the fittest.
C) evolution involving the accumulation of point mutations in viral genes.
D) punctuated equilibrium of the viral genes.

Question 26

In horizontal gene transfer a gene can be transferred between

A) two different chromosomes within an individual.
B) mother and daughter cell during replication.
C) a virus and the host genome.
D) two daughter cells during replication.

Question 27

Rickettsia is a genus of bacteria causing serious infections in humans. Rickettsia reproduce inside of human cells, and they are dependent upon the host cell's machinery to do so. Like a virus, once replicated, Rickettsia are released from the host cell and can then go on to infect other cells. For Rickettsia to be considered a virus rather than a bacterium, what properties must it have?

A) contain proteins, RNA, or DNA
B) be reliant upon the host cell's protein, RNA, and DNA synthesis machinery
C) reproduce by budding
D) cause a specific disease

Question 28

The mitochondrial RNA polymerase of human cells is related to the T7 bacteriophage RNA polymerase. This appears, therefore, to be a case of

A) viral infection.
B) horizontal gene transfer.
C) evolution.
D) prion infection.

Question 29

A viroid is

A) a very small virus with no genome.
B) a virus with a very small genome of ssDNA.
C) a naked RNA molecule that infects animals and plants.
D) a naked RNA molecule that infects plants.

Question 30

Prion diseases

A) do not infect humans.
B) are caused by mRNA.
C) affect primarily liver tissue.
D) are caused by misfolded proteins.

Question 31

Which of the following is a method for the transmission of prion diseases?

A) inhalation of airborne particles
B) consuming foods infected with the prion virus
C) consuming material that contains prions
D) contact between aerosolized particles and mucous membranes

Question 32

Label the indicated parts of the bacteriophage.
a. ____________________
b. ____________________
c. ____________________
d. ____________________

Question 33

In this figure, depicting the series of events during a viral infection and release from a cell, what is happening at stage 3?

A) Viral DNA is replicated.
B) Viral DNA is transcribed.
C) Viral mRNA is translated.
D) Viral mRNA is replicated.

Question 34

After reading the paragraph, answer the question(s) that follow(s).
Generally, we think of viruses as nasty little bits of business that arrive unwanted, take over our cellular functions, and then move along to their next victim. Recently, however, it was discovered that the human genome actually contains about half a million 'viral fossils.' Indeed, about 8% of human DNA appears to originate from viral DNA that became permanently incorporated into the human genome. And furthermore, in some cases, identical viral fossils have been found in the chimpanzee genome. These incredible findings suggest that we might need to take a broader view of how viruses and people truly interact and have done over the millennia.

-Based on these observations we might conclude that, were we able to wipe out all viruses from the face of the earth, then

A) the human race would be better off.
B) we would be removing a source of genetic variability.
C) we would rid our cells of these half a million viral DNA 'fossils.'
D) we would never be sick again.

Question 35

After reading the paragraph, answer the question(s) that follow(s).
Generally, we think of viruses as nasty little bits of business that arrive unwanted, take over our cellular functions, and then move along to their next victim. Recently, however, it was discovered that the human genome actually contains about half a million 'viral fossils.' Indeed, about 8% of human DNA appears to originate from viral DNA that became permanently incorporated into the human genome. And furthermore, in some cases, identical viral fossils have been found in the chimpanzee genome. These incredible findings suggest that we might need to take a broader view of how viruses and people truly interact and have done over the millennia.

-These observations also suggest that

A) humans and viruses have been coevolving in a relatively stable way for much of the history our species.
B) humans and chimpanzees have been separately infected by the same virus at different times in their evolutionary past.
C) viral DNA is unable to access egg or sperm cells; rather, viruses can only attack nongerm cells.
D) viruses are actually relative new phenomena that likely did not exist in the earliest stages of human evolution.