23 Questions
Which of the following is NOT a criteria for classification of viruses?
Cellular structure
What is the difference between +ssRNA and -ssRNA?
The orientation of the RNA strand
What is the key enzyme involved in retrovirus function?
Reverse transcriptase
Which of the following is NOT a component of a virus?
Cell membrane
What are the three forms of a capsid?
Helical, icosahedral, complex
What is the difference between virulent and temperate phages?
Virulent phages always cause lytic infections, while temperate phages can cause both lytic and lysogenic infections
What is uncoating in the context of viral replication?
The process of disassembly of the viral capsid
How do enveloped and non-enveloped viruses differ in terms of penetration?
Enveloped viruses enter the host cell through fusion with the host cell membrane, while non-enveloped viruses enter the host cell through receptor-mediated endocytosis
What is a retrovirus?
A virus that uses reverse transcriptase to convert its RNA genome into DNA
How are animal viruses cultivated?
In both fertilized chicken eggs and cell cultures
How are bacteriophages cultivated?
In bacterial cultures
What are plaques in the context of viral replication?
Clear zones on a lawn of host cells indicating areas of viral infection and cell death
How do scientists detect viruses?
By observing cytopathic effects such as syncytia and cell inclusions
Which of the following is NOT a step of bacteriophage replication?
Uncoating
What is the difference between +ssRNA and -ssRNA?
The polarity of the RNA strand
What is a bacteriophage?
A virus that infects bacteria
What would cause a temperate phage to switch to the lytic cycle?
Presence of certain environmental conditions
What is meant by host range?
The number of different host organisms a virus can infect
What are the criteria for classification of viruses?
Host organism, morphology, genome type
What is a viral growth curve?
A graphical representation of the different stages of viral infection in a host
How are animal viruses cultivated?
Fertilized chicken eggs, cell cultures
What are virioids?
Small infectious RNA molecules
What are virusoids?
Small infectious RNA molecules
Study Notes
Virus Classification
- Criteria for classification of viruses do not include shape, size, and other physical characteristics.
RNA Viruses
- +ssRNA viruses have a single-stranded RNA molecule that can act as messenger RNA, while -ssRNA viruses have a single-stranded RNA molecule that must be transcribed into mRNA.
- Retroviruses are a type of -ssRNA virus that uses the reverse transcriptase enzyme to convert its RNA genome into DNA.
Virus Structure
- A virus does not have a cellular membrane.
- The three forms of a capsid are helical, icosahedral, and complex.
Phages
- Virulent phages always cause lysis, whereas temperate phages can enter a dormant state, called lysogeny.
- Uncoating is the process of removing the viral protein coat, allowing the viral genome to be released into the host cell.
Penetration
- Enveloped viruses use membrane fusion to penetrate the host cell, while non-enveloped viruses use receptor-mediated endocytosis.
Virus Cultivation
- Animal viruses are cultivated in cell culture or in embryonated eggs.
- Bacteriophages are cultivated in bacterial cultures.
Virus Detection
- Viruses are detected through various methods, including observation of cytopathic effects, hemagglutination, and PCR.
- Plaques are areas of lysed bacteria on an agar plate, used to quantify bacteriophages.
Bacteriophage Replication
- A step that is not part of bacteriophage replication is binary fission.
Retroviruses
- A retrovirus is a type of virus that converts its RNA genome into DNA, which is then integrated into the host genome.
Host Range
- Host range refers to the range of species that a virus can infect.
Viral Growth Curve
- A viral growth curve is a graphical representation of the growth of a virus over time, showing the stages of eclipse, latent, and lytic phases.
Other
- Viroids are small, single-stranded RNA molecules that infect plants, lacking a protein coat.
- Virusoids are small, single-stranded RNA molecules that are dependent on a helper virus for replication.
Test your knowledge on viruses and their characteristics with this informative quiz. Learn about the components of a virus, such as the protein coat, nucleic acid, and envelope. Explore the different forms of a capsid and understand the concept of host range. Discover the criteria for classifying viruses based on host organism, morphology, and genome type. Challenge yourself and expand your understanding of these fascinating microorganisms.
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