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Questions and Answers
What is a defining characteristic of viruses in terms of their replication?
What is a defining characteristic of viruses in terms of their replication?
- They replicate only inside the living cells of a host organism. (correct)
- They reproduce independently of host cells.
- They can replicate using their own energy metabolism.
- They contain ribosomes for protein synthesis.
Which of the following features differentiates viruses from bacteria?
Which of the following features differentiates viruses from bacteria?
- Presence of single nucleic acid (correct)
- Ability to grow independently
- Enzymatic energy metabolism
- Presence of ribosomes
Which of the following statements is true about the immune response to viruses?
Which of the following statements is true about the immune response to viruses?
- Prions do not trigger an immune response.
- Viruses do not elicit any immune response.
- Bacteria trigger a stronger immune response than viruses.
- Viruses can provoke an immune response. (correct)
What substance is lacking in the structure of viruses, which is essential for their function?
What substance is lacking in the structure of viruses, which is essential for their function?
In what way are prions fundamentally different from viruses?
In what way are prions fundamentally different from viruses?
Which of the following is NOT a characteristic feature of viruses?
Which of the following is NOT a characteristic feature of viruses?
How do viruses acquire the capability to reproduce?
How do viruses acquire the capability to reproduce?
What is implied by the absence of ribosomes in viruses?
What is implied by the absence of ribosomes in viruses?
What is the first critical step for a virus to initiate infection in a host cell?
What is the first critical step for a virus to initiate infection in a host cell?
Which process describes the method by which enveloped viruses enter host cells?
Which process describes the method by which enveloped viruses enter host cells?
After attachment, how does a virus typically enter a cell?
After attachment, how does a virus typically enter a cell?
What does the term 'uncoating' refer to in the viral life cycle?
What does the term 'uncoating' refer to in the viral life cycle?
What determines the host range and tissue tropism of viral species?
What determines the host range and tissue tropism of viral species?
Which of the following statements about viral receptor binding is correct?
Which of the following statements about viral receptor binding is correct?
What role does acidification of vesicles play in viral entry into cells?
What role does acidification of vesicles play in viral entry into cells?
Which type of viral entry allows direct introduction of viral genomes into the cytoplasm?
Which type of viral entry allows direct introduction of viral genomes into the cytoplasm?
What is a disadvantage of using specific phages for bacterial infections?
What is a disadvantage of using specific phages for bacterial infections?
Which of the following statements regarding mycoviruses is true?
Which of the following statements regarding mycoviruses is true?
Which clinical issue can phage therapy address effectively?
Which clinical issue can phage therapy address effectively?
What is a cytopathic effect (CPE) observed during viral infections?
What is a cytopathic effect (CPE) observed during viral infections?
What occurs during the formation of inclusion bodies in virus-infected host cells?
What occurs during the formation of inclusion bodies in virus-infected host cells?
What is a common outcome of viral infection in host cells?
What is a common outcome of viral infection in host cells?
Cell fusion caused by some viral infections results in what phenomenon?
Cell fusion caused by some viral infections results in what phenomenon?
How do phages improve their chances of success in treating bacterial infections?
How do phages improve their chances of success in treating bacterial infections?
What is the primary purpose of using a bicarbonate buffering system in cell culture medium?
What is the primary purpose of using a bicarbonate buffering system in cell culture medium?
What is the typical duration for incubating cell cultures when suspecting viral presence?
What is the typical duration for incubating cell cultures when suspecting viral presence?
Which of the following is NOT a characteristic of primary cell cultures?
Which of the following is NOT a characteristic of primary cell cultures?
What does a cytopathic effect (CPE) indicate during cell culture inspection?
What does a cytopathic effect (CPE) indicate during cell culture inspection?
Which type of cell culture can be indefinitely maintained through serial subculture?
Which type of cell culture can be indefinitely maintained through serial subculture?
Which of the following cell lines is derived from a human carcinoma?
Which of the following cell lines is derived from a human carcinoma?
What kind of cells are utilized for the production of vaccines?
What kind of cells are utilized for the production of vaccines?
Which of the following statements about phenol red is accurate?
Which of the following statements about phenol red is accurate?
What is the role of endolysin in the lytic cycle of bacteriophages?
What is the role of endolysin in the lytic cycle of bacteriophages?
In what phase does the bacteriophage inject its genetic material into the host cell during the lytic cycle?
In what phase does the bacteriophage inject its genetic material into the host cell during the lytic cycle?
During which stage of the lytic cycle does the phage DNA/RNA commandeer the host cell's machinery?
During which stage of the lytic cycle does the phage DNA/RNA commandeer the host cell's machinery?
What happens to the host cell at the completion of the lytic cycle?
What happens to the host cell at the completion of the lytic cycle?
Which component does NOT assemble during the replication stage of the lytic cycle?
Which component does NOT assemble during the replication stage of the lytic cycle?
What distinguishes the lysogenic cycle from the lytic cycle?
What distinguishes the lysogenic cycle from the lytic cycle?
What triggers the transition from the lysogenic cycle back to the lytic cycle?
What triggers the transition from the lysogenic cycle back to the lytic cycle?
Which of the following viruses acquires its envelope from the nuclear membrane?
Which of the following viruses acquires its envelope from the nuclear membrane?
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Study Notes
Definition and Characteristics of Viruses
- A virus is an ultramicroscopic infectious agent that replicates only inside living cells of an organism.
- Viruses infect a wide range of life forms, including animals, plants, and microorganisms such as bacteria and archaea.
- Found in nearly every ecosystem on Earth, viruses are the most numerous biological entities.
- All viruses are potentially infectious and possess a single type of nucleic acid.
- Viruses cannot grow independently and rely solely on the host for reproduction.
- Lack enzymes for energy metabolism, ribosomes, and necessary genetic information for enzyme and ribosomal protein synthesis.
Differences Among Viruses, Bacteria, Fungi, and Prions
- Viruses require a host for reproduction, while prions lead to long-lasting diseases without inducing immune responses.
- Viruses attach to specific receptors on host cells to initiate infection, with interactions determining host range and tissue tropism.
- Penetration into host cells varies: receptors-mediated endocytosis, fusion of the viral envelope, or direct introduction of viral genomes.
Bacterial and Viral Interactions
- Bacteriophages are viruses that infect bacteria, utilizing two main reproduction cycles: the lytic cycle and the lysogenic cycle.
- Lytic Cycle involves:
- Attachment to bacterial surface proteins and injection of phage DNA/RNA.
- Host cell's organelles are commandeered to produce viral proteins and new phage particles.
- Host cell lysis releases new phages to infect other bacteria.
- Lysogenic Cycle allows phages to integrate their genome into the host DNA, replicating passively through host cell divisions.
Mycoviruses and Fungal Interactions
- Mycoviruses are viruses that selectively infect fungi and have been recognized since the 1960s.
Effects of Viral Activities on Host Cells
- Viral infection can lead to cytopathic effects, altered cell functions, or host cell proliferation.
- Cytopathic Effects (CPE) result from viral lysis of host cells, visible as clear zones or plaques.
- Inclusion Bodies formed during viral replication may help diagnose infections like smallpox or poliomyelitis.
- Some infections cause Cell Fusion, resulting in merged infected cells, detectable through specific culture conditions.
Cell Culture Techniques for Virus Study
- Primary Cell Cultures: Normal cells from animals or humans that grow limited passages, essential for virus isolation and vaccine production. Examples include monkey kidney and human amnion cell cultures.
- Continuous Cell Lines: Derived from cancer cells, enabling indefinite serial culture, useful for viral identification but not for vaccine production. Examples include HeLa and Vero cell lines.
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