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Questions and Answers
Which of the following is the correct definition of a virion?
Which of the following is the correct definition of a virion?
What is the role of the capsid in a virion?
What is the role of the capsid in a virion?
Which type of virus contains an outer layer of protein plus lipid?
Which type of virus contains an outer layer of protein plus lipid?
What determines the length and width of a rod-shaped virus?
What determines the length and width of a rod-shaped virus?
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What is the simplest number of capsomeres per face in a spherical virus with icosahedral symmetry?
What is the simplest number of capsomeres per face in a spherical virus with icosahedral symmetry?
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What is the primary component of the envelope in enveloped viruses?
What is the primary component of the envelope in enveloped viruses?
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What are the five main steps of the viral life cycle?
What are the five main steps of the viral life cycle?
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Which enzyme forms a small pore in the peptidoglycan of the E. coli cell wall?
Which enzyme forms a small pore in the peptidoglycan of the E. coli cell wall?
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What happens within a minute after T4 entry into a host cell?
What happens within a minute after T4 entry into a host cell?
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Which proteins are encoded by the T4 genome and required for DNA replication?
Which proteins are encoded by the T4 genome and required for DNA replication?
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What happens during the middle phase of T4 infection?
What happens during the middle phase of T4 infection?
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What is the term for the period following attachment during which infectious virions cannot be detected in the growth medium?
What is the term for the period following attachment during which infectious virions cannot be detected in the growth medium?
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How is the titer of infectious virions determined in a plaque assay?
How is the titer of infectious virions determined in a plaque assay?
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What is the term for the ability of a virus to alternate between a lytic pathway and a lysogenic pathway?
What is the term for the ability of a virus to alternate between a lytic pathway and a lysogenic pathway?
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Which of the following best describes a virus?
Which of the following best describes a virus?
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What is the size range of most viruses?
What is the size range of most viruses?
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Which of the following is NOT a type of infection caused by viruses?
Which of the following is NOT a type of infection caused by viruses?
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What is the role of a host cell in virus replication?
What is the role of a host cell in virus replication?
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Which of the following is NOT a characteristic of viral genomes?
Which of the following is NOT a characteristic of viral genomes?
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What happens during a lytic infection?
What happens during a lytic infection?
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What is the consequence of a latent infection in animal cells?
What is the consequence of a latent infection in animal cells?
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What is the consequence of a persistent infection in animal cells?
What is the consequence of a persistent infection in animal cells?
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Where is most of Earth's genetic diversity found?
Where is most of Earth's genetic diversity found?
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What is the only viral genome that is able to translate immediately upon entering the host cell?
What is the only viral genome that is able to translate immediately upon entering the host cell?
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What enzyme in retrovirus allows RNA to go to DNA?
What enzyme in retrovirus allows RNA to go to DNA?
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In retrovirus, the flow of genetic information after infection occurs in 'reverse'; that is, is flows from:
In retrovirus, the flow of genetic information after infection occurs in 'reverse'; that is, is flows from:
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Which is not an infection caused by animal cell viruses?
Which is not an infection caused by animal cell viruses?
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The process where virions come from budding of cell membrane without the final result of lysis of animal host cell is called what infection?
The process where virions come from budding of cell membrane without the final result of lysis of animal host cell is called what infection?
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Study Notes
Viral Structure and Composition
- A virion is a complete and infectious virus particle that consists of a genome surrounded by a protein shell called the capsid.
- The capsid plays a crucial role in protecting the viral genome and facilitating the attachment of the virus to its host cell.
Enveloped Viruses
- Enveloped viruses possess an outer layer of protein plus lipid, known as the envelope, which is acquired from the host cell membrane during budding.
Viral Shapes and Symmetry
- The length and width of a rod-shaped virus are determined by the alignment of its protein subunits.
- In a spherical virus with icosahedral symmetry, the simplest number of capsomeres per face is three.
Viral Envelope
- The primary component of the envelope in enveloped viruses is lipid bilayer, which is derived from the host cell membrane.
Viral Life Cycle
- The five main steps of the viral life cycle are: attachment, penetration, uncoating, replication, and lysis.
Bacteriophage T4
- The enzyme lysozyme forms a small pore in the peptidoglycan of the E. coli cell wall.
- Within a minute after T4 entry into a host cell, the host cell's translation machinery is shut down.
- The proteins encoded by the T4 genome and required for DNA replication are the T4 polymerase and helicase.
- During the middle phase of T4 infection, the viral DNA is replicated, and the host cell's metabolism is altered to support viral replication.
- The period following attachment during which infectious virions cannot be detected in the growth medium is known as the eclipse phase.
Plaque Assay
- The titer of infectious virions is determined in a plaque assay by counting the number of plaques formed on a lawn of host cells.
Viral Infections
- The ability of a virus to alternate between a lytic pathway and a lysogenic pathway is known as tropism.
- A virus is a small infectious agent that requires a host cell to replicate.
- The size range of most viruses is between 20-400 nanometers.
Host Cell Role
- The role of a host cell in virus replication is to provide the necessary machinery and resources for viral replication.
Viral Genomes
- One characteristic of viral genomes is that they are not capable of translating their genetic material into proteins immediately upon entering the host cell, except for the positive-sense RNA viruses.
Types of Infections
- A lytic infection results in the lysis of the host cell, whereas a latent infection in animal cells results in the integration of the viral genome into the host cell genome, allowing the virus to establish a long-term infection.
- A persistent infection in animal cells results in the continuous production of viral particles without killing the host cell.
- Plant viruses are not known to cause latent or persistent infections.
Genetic Diversity
- Most of Earth's genetic diversity is found in viruses.
Retroviruses
- The only viral genome that is able to translate immediately upon entering the host cell is the positive-sense RNA genome.
- The enzyme reverse transcriptase in retroviruses allows RNA to be converted into DNA.
- In retroviruses, the flow of genetic information after infection occurs in 'reverse', flowing from RNA to DNA.
- Chronic infections are not caused by animal cell viruses.
- The process where virions come from budding of cell membrane without the final result of lysis of the animal host cell is called a persistent infection.
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Description
Test your knowledge on the T4 bacteriophage life cycle and its interactions with E. coli cells. Learn about the lysozyme-like enzyme, DNA replication, transcription, translation, and more.