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NurseDive Free Nursing Practice Question
Viruses are classified by all of the following characteristics, except
A. shape
shape: Viruses are classified by their capsid shape, which may be helical, icosahedral, or complex. This structural feature is a key criterion in viral taxonomy.
B. type of nucleic acid
type of nucleic acid: Viral classification depends on whether the genome is DNA or RNA, single-stranded or double-stranded, and positive- or negative-sense.
C. size
size: The physical size of viruses, ranging from about 20 nm to 300 nm, is one of the factors used in classification.
D. ribosome size
ribosome size: Viruses do not contain ribosomes, as they rely on the host cell’s protein synthesis machinery. Therefore, ribosome size is not a characteristic used in viral classification.
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Full Explanation
A. shape: Viruses are classified by their capsid shape, which may be helical, icosahedral, or complex. This structural feature is a key criterion in viral taxonomy.
B. type of nucleic acid: Viral classification depends on whether the genome is DNA or RNA, single-stranded or double-stranded, and positive- or negative-sense.
C. size: The physical size of viruses, ranging from about 20 nm to 300 nm, is one of the factors used in classification.
D. ribosome size: Viruses do not contain ribosomes, as they rely on the host cell’s protein synthesis machinery. Therefore, ribosome size is not a characteristic used in viral classification.
Similar Questions
What is the correct order for the stages of a lytic replication cycle, from earliest to latest stages?
A. Synthesis
Synthesis: After entry, the viral genome directs the host cell machinery to synthesize viral nucleic acids and proteins. This step comes after attachment and entry, not at the beginning.
B. Assembly
Assembly: Once viral components are synthesized, they are assembled into complete virions. This occurs later in the cycle, just before release.
C. Attachment
Attachment: The first step is the virus binding to specific receptors on the host cell surface, initiating infection. This allows the virus to target a suitable host cell.
D. Entry
Entry: After attachment, the viral nucleic acid or entire virion enters the host cell through mechanisms like endocytosis or membrane fusion. This is the second step.
E. Release
Release: The final stage is when mature virions exit the host cell, often by lysis in bacteriophages or budding in enveloped viruses, enabling them to infect new cells.
Full Explanation
A. Synthesis: After entry, the viral genome directs the host cell machinery to synthesize viral nucleic acids and proteins. This step comes after attachment and entry, not at the beginning.
B. Assembly: Once viral components are synthesized, they are assembled into complete virions. This occurs later in the cycle, just before release.
C. Attachment: The first step is the virus binding to specific receptors on the host cell surface, initiating infection. This allows the virus to target a suitable host cell.
D. Entry: After attachment, the viral nucleic acid or entire virion enters the host cell through mechanisms like endocytosis or membrane fusion. This is the second step.
E. Release: The final stage is when mature virions exit the host cell, often by lysis in bacteriophages or budding in enveloped viruses, enabling them to infect new cells.
A ____________ is a clear zone on a bacterial lawn where cells have been killed by the
A. activity of a bacteriophage.
activity of a bacteriophage: This describes the cause of the clear zone, since bacteriophages infect and lyse bacterial cells, but it is not the correct term used for the zone itself.
B. colony
colony: A colony is a visible cluster of bacterial cells originating from a single progenitor cell, not a clear zone caused by viral lysis.
C. plaque
plaque: A plaque is the clear area formed on a bacterial lawn where bacteriophages have infected and destroyed bacterial cells. It represents viral activity and spread.
D. lawn
lawn: A lawn refers to the uniform layer of bacterial growth on the agar surface, which serves as the background where plaques can be observed.
E. culture
A culture is the overall growth of microorganisms in a medium, not the specific clear zone produced by bacteriophage activity.
Full Explanation
A. activity of a bacteriophage: This describes the cause of the clear zone, since bacteriophages infect and lyse bacterial cells, but it is not the correct term used for the zone itself.
B. colony: A colony is a visible cluster of bacterial cells originating from a single progenitor cell, not a clear zone caused by viral lysis.
C. plaque: A plaque is the clear area formed on a bacterial lawn where bacteriophages have infected and destroyed bacterial cells. It represents viral activity and spread.
D. lawn: A lawn refers to the uniform layer of bacterial growth on the agar surface, which serves as the background where plaques can be observed.
E. culture: A culture is the overall growth of microorganisms in a medium, not the specific clear zone produced by bacteriophage activity.
Prions are composed of
A. protein only.
protein only: Prions are infectious agents made entirely of misfolded proteins without nucleic acids. They propagate by inducing normal cellular proteins to misfold, leading to neurodegenerative diseases.
B. an RNA surrounded by a protein capsid.
an RNA surrounded by a protein capsid: This describes a typical RNA virus, not a prion. Viruses contain nucleic acids, while prions lack them completely.
C. circular RNA only.
circular RNA only: Circular RNA molecules are found in viroids, which infect plants, but prions are distinct as they are composed solely of protein.
D. circular DNA only.
circular DNA only: Circular DNA is present in some viruses and plasmids, but prions do not contain DNA or any form of nucleic acid.
Full Explanation
A. protein only: Prions are infectious agents made entirely of misfolded proteins without nucleic acids. They propagate by inducing normal cellular proteins to misfold, leading to neurodegenerative diseases.
B. an RNA surrounded by a protein capsid: This describes a typical RNA virus, not a prion. Viruses contain nucleic acids, while prions lack them completely.
C. circular RNA only: Circular RNA molecules are found in viroids, which infect plants, but prions are distinct as they are composed solely of protein.
D. circular DNA only: Circular DNA is present in some viruses and plasmids, but prions do not contain DNA or any form of nucleic acid.