Chapter 7: Viruses and Prions Flashcards
Which terms are accurate when describing viruses? (Select all that apply)
A. Alive or dead
B. Active or inactive
C. Infectious or non-infectious
D. Replicative or non-replicative
B. Active or inactive: Describes whether a virus is currently engaging in the process of infection and replication or not.
C. Infectious or non-infectious: Indicates whether a virus can or cannot cause infection in a host.
D. Replicative or non-replicative: Refers to whether a virus is in a state where it can replicate inside host cells.
Which cellular organisms can viruses infect?
A. fungi
B. animals
C. plants
D. other viruses
E. bacteria
F. protozoa
A. fungi
B. animals
C. plants
E. bacteria
F. protozoa
Reason: D. other viruses is incorrect because viruses are not cellular organisms, though they can be infected by other viruses.
True or false: Viruses are among the smallest infective agents.
A. True
B. False
A. True
Reason: Most viruses are 1000X smaller than bacteria.
How are temperate phages replicated?
A. The phage takes over the replication machinery of the host cell.
B. The phage uses its replication enzymes to create new particles.
C. The phage is replicated along with the host cell’s genome.
D. The phage moves from host cell to host cell.
C. The phage is replicated along with the host cell’s genome.
Reason: Temperate phages insert into the bacterial chromosome as a prophage. As the bacterium divides, its replicates its genome including the prophage. Therefore, all daughter cells of the original infected bacterium carry a copy of the prophage.
An infection in animals similar to a lysogeny in bacteria is called a/an _________blank infection.
A. cytopathic
B. persistent
C. oncogenic
D. transforming
B. persistent
Reason: Some animal viruses are harbored by their host cells for several weeks or up to a lifetime. These are called persistent infections
The activation of a prophage to enter the lytic cycle is called:
A. maturation
B. adsorption
C. repression
D. conversion
E. induction
E. induction
Reason: Activation of a prophage to progress into viral replication and the rest of the lytic cycle is called induction.
Both lytic and lysogenic cycles eventually lead to bacterial host cell damage.
A. True
B. False
A. True
Reason: Both are forms of parasitism, with the lysogeny representing a less deadly form.
How does lysogeny affect humans?
A. The phage can be released from an infectious bacterial cell and infect human host cells instead.
B. Bacteria can become virulent due to phage genes, causing greater damage to infected human host.
C. The phage causes significant changes to host cell division, leading to cancer.
B. Bacteria can become virulent due to phage genes, causing greater damage to infected human host.
Reason: Some bacteria become pathogenic because they carry phage genes that code for toxins or enzymes that affect the human host. Examples include the bacteria that cause cholera, botulism, and diphtheria.
Choose the term that describes a virus that has a membranous outer covering over its capsid.
A. Naked virus
B. Enveloped virus
C. Icosahedral virus
D. Coated virus
E. Encapsulated virus
B. Enveloped virus
Reason: This membranous covering is called an envelope, and viruses which have such a covering are called “enveloped” viruses. A virus which lacks this covering is referred to as a “naked” virus. Enveloped viruses acquire their membranous coverings as they bud off the host cell membrane or from membranous organelles inside the host cell. However, the virus does place its own proteins into the envelope. Therefore, the envelope is partially derived from the host cell but does differ from the host cell membrane.
Choose the phrase that best describes the role of viral surface proteins or spikes.
A. Provide means of attachment to host cell surface
B. Provide means for viruses to exchange nucleic acid
C. Enable replication of the viral nucleic acid
D. Allow viruses to bind to each other
E. Inject viral nucleic acid into host cell
A. Provide means of attachment to host cell surface
Reason: Many viruses have surface proteins that project outward from the capsid or envelope. These proteins provide a means for the virus to attach to a host cell, the first step in establishing an infection.
Choose the term that describes a bacteriophage infection in which the host bacteria are lysed and killed by the infection.
A. Lysogenic
B. Hemorrhagic
C. Oncogenic
D. Lytic
E. Transforming
D. Lytic
Reason: A lytic infection occurs when a bacteriophage infects bacteria, and the bacteria are ruptured or lysed as a result of the infection.
The majority of human viral infections are fatal.
A. True
B. False
B. False
Reason: Most viral infections do not result in death, although there are some viruses (Ebola, rabies) which have a very high mortality.
Select the infectious agents that are noncellular.
A. Bacteria
B. Prions
C. Satellite viruses
D. Protozoa
E. Viroids
B. Prions
C. Satellite viruses
E. Viroids
Reason: In addition to viruses, there are several other noncellular infectious agents. These include prions, satellite viruses, and viroids. Prions are abnormal protein fibrils. Satellite viruses are those that require co-infection with another virus for replication. Viroids are RNA strands without a capsid that parasitize and destroy many types of plants.
A portion of the viral envelope comes from the cell membrane of the host cell.
A. True
B. False
A. True
In the release process, the viral capsid:
A. engulfs the viral spikes.
B. surrounds the viral matrix protein.
C. becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.
D. is dissolved.
C. becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.
