16 Questions
What is the purpose of staining cells in a plaque assay?
To visualize plaques, which appear clear
Why are red blood cells commonly used for assaying viruses?
They have carbohydrate-containing receptors on their surface, to which a number of animal viruses bind
What is the result of binding an excess of virus with red blood cells in a hemagglutination assay?
Agglutination (clumping) of red blood cells
What causes a clearing of the bacterial culture in a plaque assay?
Lysis of bacterial cells by bacteriophages
What method is used to visualize virus particles, which appear as light images against a dark background due to negative staining?
Electron microscopy
How are virus replication cycles studied using the MOI (Multiplicity of Infection)?
By infecting 10^3-10^6 cells with an excess of virus to ensure each cell receives at least one infectious particle
What is the initial drop in infectious titer due to in virus replication cycles?
Defective particles and uncoating inside the host cell
How are virions classified based on the system developed by David Baltimore?
Into seven groups
What do capsids of viruses provide in terms of genetic economy and self-assembly?
Composed of many copies of identical subunits
What defines the symmetry of helical capsids in viruses?
The number of subunits per turn and the displacement along the helical axis between subunits
What is the role of identical subunits in capsids of viruses?
Providing genetic economy and self-assembly
How do viruses transmit RNA or DNA genomes efficiently?
With a rigid, symmetrical capsid and enclosed viral genome
What determines the symmetry of identical subunits in capsids of viruses?
Tetrahedral, cubic, or icosahedral symmetry
How is the genome of negative strand RNA viruses accommodated within helical capsids?
The genome winds along a groove that follows a helical path of protein subunits
What method is used to track virus entry into cells?
Fluorescence microscopy
What is the purpose of studying virus replication cycles using the MOI (Multiplicity of Infection)?
To ensure each cell receives at least one infectious particle
Study Notes
Virus Replication and Structure Overview
- Not all virus particles are infectious, as disrupted or defective virions, empty capsids, and cellular anti-viral defenses can interfere with virus replication
- Electron microscopy is used to visualize virus particles, which appear as light images against a dark background due to negative staining
- Virus replication cycles are studied using the MOI (Multiplicity of Infection) by infecting 10^3-10^6 cells with an excess of virus to ensure each cell receives at least one infectious particle
- The initial drop in infectious titer is due to defective particles and uncoating inside the host cell
- Analysis of viral macromolecules can reveal detailed pathways of virus replication, which vary greatly depending on host cell, viral genome, and virus complexity
- Virus replication cycles involve attachment to a host cell, entry into the host cell, genome replication and gene expression, assembly and morphogenesis, and release/exit
- Viruses can be divided into seven groups based on the system developed by David Baltimore
- Virions have evolved structures to efficiently transmit RNA or DNA genomes, with a rigid, symmetrical capsid and enclosed viral genome
- Capsids are composed of many copies of identical subunits, providing genetic economy and self-assembly
- Identical subunits can have tetrahedral, cubic, or icosahedral symmetry, with helical nucleocapsids accommodating variable genome lengths
- Helical capsids' symmetry is defined by the number of subunits per turn and the displacement along the helical axis between subunits
- For negative strand RNA viruses, the genome winds along a groove that follows a helical path of protein subunits, with each protein subunit binding a fixed number of nucleotides
Test your knowledge of virus replication and structure with this quiz. Explore topics such as electron microscopy, virus replication cycles, viral macromolecules, viral classification, and virion structures. Understand the intricate pathways of virus replication and the evolution of virions' structures to transmit RNA or DNA genomes efficiently.
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