Chapter 13 Problem Set
Which of the following descriptions fits a chronic viral infection?
Characterized by continuous production of low levels of viral particles, potentially even in the absence of active symptoms of disease. The organism is usually still highly infectious during this time.
What bacterial enzyme is used by the virus for replicating its nucleic acid?
DNA polymerase
Which of the following about viruses/viral infections is FALSE?
Phages often enter a cell via receptor-mediated endocytosis.
Viruses with which characteristic would be expected to have a higher mutation rate?
RNA genome
T or F: The enzyme lysozyme is used by the T4 phage to assist in the injection of its DNA into the target cell.
True
T or F: bacteriophage DNA directs the degradation of the bacterial host cell's DNA
True
The stage of T4 replication that involves interaction between the protein fibers on the phage and receptors on the bacterial cell wall is the
attachment stage
Every virus particle contains ______.
either DNA or RNA
The mechanism of exit for an animal virus is primarily determined by whether or not the virus has a(n) _____.
envelope
A major difference in the replication of animal viruses and bacteriophages is the ______ step.
penetration
Viral capsids are composed of
protein
Phage DNA encodes for the proteins of the viral capsid and
regulatory proteins that direct the production and assembly of the capsid proteins.
All of the following could serve as receptors for phage attachment EXCEPT
ribosomes
In viral entry by endocytosis
the host cell's cytoplasmic membrane surrounds the whole virion and forms a vesicle.
Which of the following can cause a phage in the lysogenic stage to revert to the lytic stage?
ultraviolet light
Removal of the capsid to release the virus nucleic acid into the host cytoplasm is called ______.
uncoating
Rabies virus, which can be transmitted from animals to humans, is classified as a(n) ______ virus.
zoonotic
Please choose the term that describes a virus that has a lipid bilayer (derived from the host cell) surrounding its capsid.
Enveloped virus
Expression of viral oncogenes in infected animal cells
can mimic proto-oncogenes, causing imbalance in cell cycle control towards unchecked proliferation, leading to tumor formation.
T or F: Almost immediately upon entry, the viral nucleic acid alters the gene expression of the host cell.
true
T or F: Both enveloped and non-enveloped (naked) viruses can enter a cell by endocytosis
true
The general steps in viral replication (in order) are
absorption, penetration, synthesis, assembly, release
Once inside the host cell, viral DNA directs production of _______.
new viral particles
Which of the following is used to classify viruses? i. Nucleic acid ii. Shape iii. Size iv. Host range v. Biochemical tests
(i), (ii), (iii), and (iv)
Which of the following contains only one type of macromolecule? i. RNA viruses ii. DNA viruses iii. Prions iv. Viroids v. RNA and DNA viruses
(iii) and (iv)
Which of the following is an example of lysogenic conversion?
A lysogen that acquires new characteristics as a result of the prophage.
Immunity to superinfection (infection of a cell at a later time with a second, identical bacteriophage) is a consequence of lysogeny. Why does this occur?
A repressor produced by the first virus will actively suppress the lytic cycle of the second virus.
Which of the following is required to maintain a lysogenic state?
A repressor protein
The T-even bacteriophages such as T2 and T4 infect
Escherichia coli.
T or F: In the lysogenic stage of phage replication, the host cell is lysed.
False
T or F: Once a phage becomes lysogenic, it will remain lysogenic and never be lytic again.
False
T or F: T-even phages can replicate independently of a host cell
False
How does bacteriophage DNA get into the host cell?
It is injected
Which of the following describes a latent viral infection?
Long periods of time with essentially zero viral replication, punctuated by outbreaks of active replication and disease manifestation. Infected individuals are largely non-infectious between outbreak periods.
What term describes the type of bacteriophage infection cycle where the bacteriophage DNA is inserted into the host cell DNA as a prophage and the infected bacteria can continue to grow and divide?
Lysogenic
A bacteriophage initially associates with which bacterial structure?
The bacterial cell wall
A bacterium being examined in a microbiology laboratory is found to be lysogenized by phage A. Which of the following statements is TRUE?
The bacterium exhibits a new genotype but may not exhibit a new phenotype.
Please choose the statement that best describes the role of viral surface proteins or spikes.
Viral spikes provide means of attachment to host cell surface.
A consequence of the temperate life cycle is lysogenic conversion. What does this term mean?
When a bacterial cell starts to produce a new phage protein (e.g., diphtheria toxin) after the viral genome inserts into the host genome.
The capsid of a virus is
a protein shell that surrounds the nucleic acid.
Viral spikes
attach specifically to host cell receptors.
A virus usually infects only certain types of cells due to
interactions between viral and cellular surface molecules.
The final step in T2 bacteriophage infection results in:
lysis of the bacterial cell and release of new viral particles.
Viral cycles that end in release of the new phages and immediate destruction of the host bacterial cell are referred to as ______.
lytic
What term describes the type of bacteriophage infection in which the host bacteria are lysed and killed as a result of the infection?
lytic
when present, of what is the viral envelope composed?
mainly lipids
Some phages are medically important for all of the following reasons EXCEPT
they also infect eukaryotic cells.