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Questions and Answers
What is one of the proposed origins of viruses?
What suffix is used for virus family names?
Which property is NOT mentioned as part of the physicochemical properties of virions?
Which factor is NOT included in the biologic properties of viruses?
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Which of the following best describes poxviruses?
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According to current theories, which organism type did viruses NOT evolve from?
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What is included in the classification of viruses into families?
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Which of the following components is NOT associated with viral taxonomy?
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Which characteristics describe viruses that use both DNA and RNA?
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What are viroids primarily composed of?
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Which structural feature characterizes viroids?
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Prions are infectious particles comprised solely of what?
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What is a common mechanism by which viroids replicate?
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How does cryoelectron microscopy preserve fine structural features of samples?
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What do prions lack that is typically found in other infectious agents?
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What is the first step in the viral growth cycle?
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What level of atomic resolution can X-ray crystallography typically achieve?
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Which type of viral architecture exhibits helical symmetry?
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Which of the following describes the role of the viral mRNA?
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Where does the replication of viral DNA typically occur?
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What is the primary cause of devastating plant diseases induced by viroids?
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What structure is responsible for encasing the viral genetic material?
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What is a feature of viroid RNA?
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Which component is produced after viral mRNA translation?
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What would be the final product of the viral growth cycle?
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What occurs during the eclipse period of viral infection?
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Which type of antibiotics are ineffective against viruses?
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What is required in larger concentrations to destroy viruses compared to bacteria?
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What is a characteristic of productive viral infections?
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What often occurs after viral nucleic acid enters the host cell?
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Which disinfectants are specifically mentioned as ineffective against viruses?
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The yield of infectious virus per cell can vary widely. What is the range mentioned?
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How long can the virus replication cycle last for some herpesviruses?
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What is a common characteristic of antiviral drugs compared to antibiotics?
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Why is the chlorine treatment of stools sometimes inadequate?
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What characterizes abortive infections?
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What is a common purpose for inactivating viruses?
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Which process is the first step in viral infection?
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What happens during a latent infection?
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What might an inactivated virus vaccine contain?
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What can lead to a variety of viral strategies for multiplication?
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During which step does uncoating occur in the viral replication cycle?
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Which option best defines the term 'permissive cell'?
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What is a potential outcome of an inactivated virus infection?
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Which type of viral infection could be caused by a defective virus?
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Study Notes
Evolutionary Origin of Viruses
- The exact origin of viruses remains unknown, with distinct differences observed between DNA viruses, RNA viruses, and those utilizing both genetic materials.
- Two primary theories propose origins:
- Viruses may have evolved from components of host cells capable of independent replication.
- Some viruses may represent degenerate intracellular parasites, with complex forms like poxviruses possibly indicating a unique evolutionary path.
- No evidence links viral evolution directly to bacteria, though other obligate intracellular organisms may have derived from them.
Universal System of Virus Taxonomy
- Viruses are classified into families based on virion morphology, genome structure, and replication strategies.
- Virus family names end with the suffix "-viridae".
- Within families, genera are categorized based on biological, genomic, physicochemical, or serologic differences.
Viroids
- Viroids are small infectious agents that cause plant diseases, lacking protein coats, and consist solely of circular RNA about 360 nucleotides in length.
- Viroids replicate via a unique mechanism, without encoding protein products, leading to plant diseases through unknown pathways.
Prions
- Prions consist entirely of protein without detectable nucleic acids, behaving as infectious agents.
- Some prion interactions with host cells result in rapid viral progeny accumulation, redirecting cellular metabolism towards viral synthesis.
Antibiotics and Other Antibacterial Agents
- Antibiotics are ineffective against viruses; some antiviral drugs exist for treatment.
- Common disinfectants, including certain alcohols and quaternary ammonia compounds, may not effectively inactivate viruses.
- Chlorine in larger concentrations is required to kill viruses in contaminated sources like feces.
Common Methods of Inactivating Viruses
- Viral inactivation methods are used for sterilization, disinfection, and vaccine production.
- Techniques and chemicals vary depending on the intended purpose, such as making drinking water safe or disinfecting surfaces.
General Steps in Viral Replication Cycles
- Viral replication generally follows similar patterns across different virus types, involving steps such as attachment, penetration, uncoating, and synthesis of viral components.
- Attachment initiates infection through specific receptor interactions between virus proteins and host cell surfaces.
- The viral growth cycle includes the synthesis of viral nucleic acids and proteins, followed by assembly into infectious virions.
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Description
Explore the mysterious evolutionary origins of viruses and their antigenic properties. This quiz delves into the differences between DNA and RNA viruses, as well as their physicochemical characteristics such as stability and reactivity to antisera.
