Viruses & Prions (MasteringMicro) || a+ guaranteed
Solutions.
Chlamydia trachomatis is an obligate intracellular bacterium that causes the sexually
transmitted disease chlamydia. When this bacterium was first discovered, it was classified as
a virus. However, it was later re-classified as a bacterium. Which of the following is the most
likely reason why C. trachomatis was reclassified as a living bacterial cell as opposed to a
nonliving viral particle?
a) capable of performing metabolic processes.
b) lacks membrane-bound organelles, such as a nucleus.
c) has a genome consisting of double-stranded DNA.
d) is visible with a compound light microscope. correct answers a) capable of performing
metabolic processes
Which of the following are ways that viruses differ from prokaryotes and eukaryotes? Select
all true statements.
Unlike prokaryotes and eukaryotes...
a) viruses are incapable of replicating independently from a host cell.
b) viruses do not have genomes.
c) viruses are classified as acellular particles.
d) viruses are not considered alive. correct answers Unlike prokaryotes and eukaryotes...
a) viruses are incapable of replicating independently from a host cell.
c) viruses are classified as acellular particles.
d) viruses are not considered alive.
The rabies virus primarily affects the nervous system. The specificity that the rabies virus has
for neuronal host cells is primarily dictated by __________________________.
a) the spikes that protrude from its viral envelope
b) the helical shape of its viral capsid
c) the type of nucleic acid used for its viral genome (single-stranded, antisense RNA)
d) the segmented nature of its viral genome correct answers a) the spikes that protrude from
its viral envelope
Which of the following genome types has been observed in viruses? Select all true
statements.
a) Protein-based
b) Double-stranded RNA
c) Single-stranded DNA
d) Single-stranded RNA correct answers b) Double-stranded RNA
c) Single-stranded DNA
d) Single-stranded RNA
You are studying an unknown virus that does not perform transcription to make viral
proteins. Which of the following characteristics must also be true for this unknown virus?
a) The virus has a positive, sense-stranded RNA genome.
b) The virus has a double-stranded RNA genome.
c) The viral genome must encode reverse transcriptase.
d) The viral genome must encode RNA-dependent RNA polymerases. correct answers a) The
virus has a positive, sense-stranded RNA genome.
, In the Spring of 2009, a novel H1N1 virus emerged that had a new combination of genes
from pigs, humans, and birds. As a result, the virus spread quickly, resulting in a swine flu
pandemic. Which of the following concepts explains why the outbreak occurred?
a) Narrow tropism
b) Antigenic drift
c) Attenuation
d) Antigenic shift correct answers d) antigenic shift
Viruses are considered to be non-living pathogens for which reason?
a) their extremely small size
b) their unique type of cells and their lack of metabolic processes
c) their lack of metabolic processes
d) their ability to synthesize only some of their own components
e) their unique type of cells correct answers c) their lack of metabolic processes
Compared to both prokaryotic and eukaryotic cells, viruses...
a) have similar metabolic processes.
b) lack genetic material.
c) lack proteins.
d) are generally smaller.
e) are not filterable. correct answers d) are generally smaller
Which statement is NOT true about the virus capsid?
a) The capsid functions as a package for the viral genetic material.
b) The capsid is made of one or more types of protein subunits.
c) The capsid determines the shape of the virus.
d) Both bacteriophage and animal viruses have capsids.
e) Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs
correct answers e) Because the capsid is not essential to the virus, it is not a useful target for
antiviral drugs
When a virus has an envelope,
a) it is always an RNA-containing virus.
b) it may escape its host cell either by budding or by lysis.
c) it is always a bacteriophage.
d) it likely escapes its host cell by budding.
e) it likely escapes its host cell by lysis. correct answers d) it likely escapes its host cell by
budding
Viral spikes...
a) show specificity in binding to particular structures on the host cell.
b) allow the virus to attach and enter host cells but do not show specificity for a particular
structure on the host cell.
c) may be a target for the host immune system.
d) allow the virus to attach and enter host cells.
e) allow the virus to attach and enter host cells, may be a target for the host immune system,
and show specificity in binding to particular structures on the host cell. correct answers e)
allow the virus to attach and enter host cells, may be a target for the host immune system, and
show specificity in binding to particular structures on the host cell.
Solutions.
Chlamydia trachomatis is an obligate intracellular bacterium that causes the sexually
transmitted disease chlamydia. When this bacterium was first discovered, it was classified as
a virus. However, it was later re-classified as a bacterium. Which of the following is the most
likely reason why C. trachomatis was reclassified as a living bacterial cell as opposed to a
nonliving viral particle?
a) capable of performing metabolic processes.
b) lacks membrane-bound organelles, such as a nucleus.
c) has a genome consisting of double-stranded DNA.
d) is visible with a compound light microscope. correct answers a) capable of performing
metabolic processes
Which of the following are ways that viruses differ from prokaryotes and eukaryotes? Select
all true statements.
Unlike prokaryotes and eukaryotes...
a) viruses are incapable of replicating independently from a host cell.
b) viruses do not have genomes.
c) viruses are classified as acellular particles.
d) viruses are not considered alive. correct answers Unlike prokaryotes and eukaryotes...
a) viruses are incapable of replicating independently from a host cell.
c) viruses are classified as acellular particles.
d) viruses are not considered alive.
The rabies virus primarily affects the nervous system. The specificity that the rabies virus has
for neuronal host cells is primarily dictated by __________________________.
a) the spikes that protrude from its viral envelope
b) the helical shape of its viral capsid
c) the type of nucleic acid used for its viral genome (single-stranded, antisense RNA)
d) the segmented nature of its viral genome correct answers a) the spikes that protrude from
its viral envelope
Which of the following genome types has been observed in viruses? Select all true
statements.
a) Protein-based
b) Double-stranded RNA
c) Single-stranded DNA
d) Single-stranded RNA correct answers b) Double-stranded RNA
c) Single-stranded DNA
d) Single-stranded RNA
You are studying an unknown virus that does not perform transcription to make viral
proteins. Which of the following characteristics must also be true for this unknown virus?
a) The virus has a positive, sense-stranded RNA genome.
b) The virus has a double-stranded RNA genome.
c) The viral genome must encode reverse transcriptase.
d) The viral genome must encode RNA-dependent RNA polymerases. correct answers a) The
virus has a positive, sense-stranded RNA genome.
, In the Spring of 2009, a novel H1N1 virus emerged that had a new combination of genes
from pigs, humans, and birds. As a result, the virus spread quickly, resulting in a swine flu
pandemic. Which of the following concepts explains why the outbreak occurred?
a) Narrow tropism
b) Antigenic drift
c) Attenuation
d) Antigenic shift correct answers d) antigenic shift
Viruses are considered to be non-living pathogens for which reason?
a) their extremely small size
b) their unique type of cells and their lack of metabolic processes
c) their lack of metabolic processes
d) their ability to synthesize only some of their own components
e) their unique type of cells correct answers c) their lack of metabolic processes
Compared to both prokaryotic and eukaryotic cells, viruses...
a) have similar metabolic processes.
b) lack genetic material.
c) lack proteins.
d) are generally smaller.
e) are not filterable. correct answers d) are generally smaller
Which statement is NOT true about the virus capsid?
a) The capsid functions as a package for the viral genetic material.
b) The capsid is made of one or more types of protein subunits.
c) The capsid determines the shape of the virus.
d) Both bacteriophage and animal viruses have capsids.
e) Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs
correct answers e) Because the capsid is not essential to the virus, it is not a useful target for
antiviral drugs
When a virus has an envelope,
a) it is always an RNA-containing virus.
b) it may escape its host cell either by budding or by lysis.
c) it is always a bacteriophage.
d) it likely escapes its host cell by budding.
e) it likely escapes its host cell by lysis. correct answers d) it likely escapes its host cell by
budding
Viral spikes...
a) show specificity in binding to particular structures on the host cell.
b) allow the virus to attach and enter host cells but do not show specificity for a particular
structure on the host cell.
c) may be a target for the host immune system.
d) allow the virus to attach and enter host cells.
e) allow the virus to attach and enter host cells, may be a target for the host immune system,
and show specificity in binding to particular structures on the host cell. correct answers e)
allow the virus to attach and enter host cells, may be a target for the host immune system, and
show specificity in binding to particular structures on the host cell.
