Podcast
Questions and Answers
Which of the following statements concerning viruses is FALSE?
Which of the following statements concerning viruses is FALSE?
- Viruses enter a cell to complete the replication they have begun extracellularly. (correct)
- Viruses never contain both DNA and RNA.
- Tobacco mosaic virus was the first virus to be discovered and characterized.
- Viral capsids can assume one of three basic shapes.
- Some viruses have an outer membrane called an envelope.
The outermost layer of a virion fulfills which of the following functions of the virus?
The outermost layer of a virion fulfills which of the following functions of the virus?
- Protection
- Recognition and replication
- Replication
- Protection and recognition (correct)
- Recognition
During the intracellular state, a virus exists as:
During the intracellular state, a virus exists as:
- Both a lipid and a nucleic acid.
- Both a protein and a nucleic acid.
- A protein.
- A lipid.
- A nucleic acid. (correct)
Viruses are primarily classified according to their:
Viruses are primarily classified according to their:
Host specificity of a virus is due to:
Host specificity of a virus is due to:
Who was the first person to demonstrate the existence of viruses?
Who was the first person to demonstrate the existence of viruses?
How are fungal viruses different from viruses that infect other organisms?
How are fungal viruses different from viruses that infect other organisms?
Which of the following infectious particles do NOT have protein in their structure?
Which of the following infectious particles do NOT have protein in their structure?
Which of the following would NOT be found as a component of a bacteriophage?
Which of the following would NOT be found as a component of a bacteriophage?
Which of the following statements regarding virus taxonomy is true?
Which of the following statements regarding virus taxonomy is true?
Which of the following statements comparing virus classification and taxonomy of organisms is true?
Which of the following statements comparing virus classification and taxonomy of organisms is true?
Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?
Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?
The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?
The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?
The phenomenon of transduction is associated with which of the stages of a bacteriophage infection cycle?
The phenomenon of transduction is associated with which of the stages of a bacteriophage infection cycle?
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but NOT in the lysogenic cycle?
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but NOT in the lysogenic cycle?
Why is lysogeny advantageous to a bacteriophage?
Why is lysogeny advantageous to a bacteriophage?
Which of the following agents is capable of inducing conversion of a prophage back to a lytic phage?
Which of the following agents is capable of inducing conversion of a prophage back to a lytic phage?
Zones of clearing in cell cultures that are the result of virus infection are called plaques. What type of viral infection might cause cloudy plaques?
Zones of clearing in cell cultures that are the result of virus infection are called plaques. What type of viral infection might cause cloudy plaques?
Which of the following is matched INCORRECTLY?
Which of the following is matched INCORRECTLY?
Reverse transcriptase is associated with which of the following?
Reverse transcriptase is associated with which of the following?
The genome of which of the following types of animal virus can act directly as mRNA?
The genome of which of the following types of animal virus can act directly as mRNA?
Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?
Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?
In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of the host cell. This fact implies that the viral genome may encode:
In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of the host cell. This fact implies that the viral genome may encode:
Which of the following membranes can give rise to a viral envelope?
Which of the following membranes can give rise to a viral envelope?
The majority of cases of infant diarrhea are caused by what kind of virus?
The majority of cases of infant diarrhea are caused by what kind of virus?
How is the HIV provirus different from a lambda phage prophage?
How is the HIV provirus different from a lambda phage prophage?
Which of the following individuals discovered prions?
Which of the following individuals discovered prions?
One mechanism by which viruses may cause cancer is to interrupt the genetic regulatory sequences of repressor proteins. Which of the following types of viruses is most likely to be involved in causing cancer by this mechanism?
One mechanism by which viruses may cause cancer is to interrupt the genetic regulatory sequences of repressor proteins. Which of the following types of viruses is most likely to be involved in causing cancer by this mechanism?
Tumors invade other organs and tissues in a process called:
Tumors invade other organs and tissues in a process called:
Plaque assays are used for:
Plaque assays are used for:
Diploid cell cultures and continuous cell cultures differ in which of the following ways?
Diploid cell cultures and continuous cell cultures differ in which of the following ways?
Viroids infect:
Viroids infect:
How are prions different from all other known infectious agents?
How are prions different from all other known infectious agents?
The infectious particles of fungi have RNA genomes and lack a capsid. They are therefore similar to:
The infectious particles of fungi have RNA genomes and lack a capsid. They are therefore similar to:
A lipid membrane is present in:
A lipid membrane is present in:
Double-stranded DNA genomes are found in:
Double-stranded DNA genomes are found in:
Double-stranded RNA genomes can be found:
Double-stranded RNA genomes can be found:
Cytoplasm is a characteristic of:
Cytoplasm is a characteristic of:
Proteins are present in:
Proteins are present in:
Viruses are shed slowly and steadily during:
Viruses are shed slowly and steadily during:
During __________, viruses remain dormant in a cell.
During __________, viruses remain dormant in a cell.
Virus replication results in the death of the cell in a(n) __________ infection.
Virus replication results in the death of the cell in a(n) __________ infection.
Virus infection results in cancer in the process of __________.
Virus infection results in cancer in the process of __________.
Is a mechanism of release for enveloped viruses.
Is a mechanism of release for enveloped viruses.
Viruses cause most human cancers.
Viruses cause most human cancers.
Most viruses cannot be seen by light microscopy.
Most viruses cannot be seen by light microscopy.
Protozoa are susceptible to viral attack.
Protozoa are susceptible to viral attack.
Many diseases of plants are caused by infectious RNA molecules lacking capsids.
Many diseases of plants are caused by infectious RNA molecules lacking capsids.
Bacteriophages are cheaper and easier to culture than animal viruses.
Bacteriophages are cheaper and easier to culture than animal viruses.
Assembly of new viruses is a process that usually requires the direction of a variety of viral and cellular enzymes.
Assembly of new viruses is a process that usually requires the direction of a variety of viral and cellular enzymes.
Bacteriophage release is a gradual process in which small numbers are released at a time.
Bacteriophage release is a gradual process in which small numbers are released at a time.
Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for the majority of dsDNA viruses.
Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for the majority of dsDNA viruses.
Transcription of RNA from RNA does not occur in uninfected cells.
Transcription of RNA from RNA does not occur in uninfected cells.
Virus vaccines are always cultured in embryonated chicken eggs.
Virus vaccines are always cultured in embryonated chicken eggs.
Study Notes
Viruses Overview
- Viruses never contain both DNA and RNA; they either have one or the other.
- Host specificity arises from interactions between viral surface molecules and cellular receptors.
- Viruses are primarily classified by their type of nucleic acid: DNA or RNA.
Virus Structure and Replication
- The outer layer of a virion (virus particle) provides both protection and recognition functions.
- The intracellular state of a virus is typically solely as nucleic acid, not as a protein or lipid.
- Viral genomes, such as double-stranded DNA (dsDNA) and double-stranded RNA (dsRNA), are found in both viruses and cells.
Virus Classification and Taxonomy
- Virus family names may derive from significant members of the family rather than the host taxonomy.
- The classification of viruses involves genus and species epithet, similar to organisms.
Infection Mechanisms
- Attachment of bacteriophages to bacterial cells involves random collisions, chemical attraction, and receptor specificity.
- Bacteriophage infection leads to the lytic cycle, which involves stages: attachment, entry, synthesis, assembly, and release.
Unique Viral Properties
- Viroids lack protein and have RNA as their genetic material, differing from classical viruses.
- Prions are unique infectious agents that consist solely of protein with no nucleic acids, causing neurological diseases.
Cancer and Viral Infection
- Certain viruses, notably retroviruses, can induce cancer by altering genetic regulatory sequences in host cells.
- The process where tumors invade other tissues is termed metastasis.
Viral Types and Their Effects
- Positive-sense single-stranded RNA (+ssRNA) viruses can act directly as mRNA.
- Negative-sense single-stranded RNA (-ssRNA) viruses require RNA-dependent RNA transcriptase for replication.
Viral Lifecycle and Effects on Host Cells
- Lytic infections result in cell death, while latent infections allow viruses to remain dormant.
- Persistent infections involve slow and steady release of viruses over time, without immediate cell death.
Methods of Study and Cultivation
- Plaque assays are utilized to estimate the number of phages in a culture by observing zones of clearing.
- Bacteriophages are more cost-effective and simpler to culture compared to animal viruses.
Vaccination and Immune Response
- Vaccines may be cultured in embryonated chicken eggs, although not exclusively.
- Understanding the mechanism of virus assembly provides insights into potential therapeutic strategies.
Additional Key Points
- Most human cancers stem from viruses, highlighting the role of viral infections in oncology.
- Many plant diseases are caused by RNA molecules that are infectious but lack protective capsids.
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Description
Explore the fascinating world of viruses, including their structure, replication, and classification. This quiz covers key concepts such as nucleic acid types, host specificity, and viral taxonomy. Test your knowledge of how viruses interact with host cells and their mechanisms of infection.
