Microbiology Test II ch13 – Flashcards

Unlock all answers in this set

Unlock answers
question
The envelope found in some virus particles differs from the cytoplasmic membrane of cells in that
answer
it does not perform the physiological functions carried out by the cytoplasmic membrane.
question
The combination of a virus's protein coat and nucleic acid core is called the ________.
answer
nucleocapsid
question
Which of the following statements concerning viruses is FALSE?
answer
Viruses enter a cell to complete the replication they have begun extracellularly.
question
The outermost layer of a virion fulfills which of the following functions of the virus?
answer
protection and recognition
question
Most viruses cannot be seen by light microscopy. T or F
answer
T
question
During the intracellular state, a virus exists as
answer
a nucleic acid.
question
Protozoa are susceptible to viral attack. T or F
answer
T
question
Viruses are primarily classified according to their
answer
type of nucleic acid.
question
Host specificity of a virus is due to
answer
interactions between viral and cellular surface molecules.
question
An animal virus that does not have an envelope is described as a(n) ________ virion.
answer
naked
question
Proteins are present in
answer
both cells and viruses
question
Cytoplasm is characteristic of
answer
cells only
question
A lipid membrane is present
answer
in both cells and viruses.
question
In which stage is the viral DNA introduced into the cell?
answer
Penetration
question
In which stage does formation of mature viruses occur?
answer
Assembly
question
The host DNA is usually degraded during which stage?
answer
Biosynthesis
question
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
answer
The virus would not be able to infect new hosts.
question
Lysogenic viral DNA integrating into the host genome is referred to as
answer
a prophage
question
Which of the following events might trigger induction of a temperate bacteriophage?
answer
Exposure to UV light
question
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
answer
The host dies during the lytic stage
question
What is the fate of the prophage during the lysogenic stage?
answer
It is copied every time the host DNA replicates.
question
How are viruses different from cells?
answer
They require a host in order to reproduce.
question
What is the function of the structural elements of a virus?
answer
To package and protect the viral genome
question
We sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. This renders the virus unable to reproduce. Which step of viral replication are antibodies directly preventing?
answer
attachment
question
Enveloped viruses have a layer of lipids surrounding their capsid. This envelope is made mostly of host cell membrane. In which step does the virus acquire this envelope?
answer
release
question
What occurs during viral uncoating?
answer
The capsid breaks apart, releasing the viral genome.
question
Bacteriophage genes that cause toxin production in a normally harmless bacterial species contribute to which of the following?
answer
lysogenic conversion
question
Infections with enveloped animal viruses are similar to lysogenic phage infections because
answer
the infected cell may live for a long time
question
Which of the following is the midpoint of a lytic replication cycle?
answer
synthesis
question
Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4?
answer
entry and release
question
You have isolated a specimen of lambda phage in which the protein that suppresses prophage genes has suffered a significant mutation. Which of the following would you expect to observe in cultures of this virus?
answer
The phage will never enter a lysogenic cycle.
question
A phage T4 particle that has lost its tail fibers will have a replication cycle that is blocked at which of the following stages
answer
attachment
question
Bacteriophages use the enzyme ________ to breach the bacterial cell wall.
answer
lysozyme
question
The number of new bacteriophages released from each infected cell is called the ________.
answer
burst size
question
Bacteriophages are cheaper and easier to culture than animal viruses T or F
answer
T
question
Another term for a lysogenic phage is a ________ phage
answer
temperate
question
Bacteriophage release is a gradual process in which small numbers are released at a time. T or F
answer
F
question
Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for the majority of dsDNA viruses. T or F
answer
T
question
RNA viruses such as HIV require the activity of ________ to become proviruses.
answer
reverse trancriptase
question
Put the following stages of a lytic replication cycle in order, from earliest to latest stages: I. Synthesis II. Assembly III. Attachment IV. Release V. Entry
answer
III. attachment V. entry I. synthesis II. assembly IV. release
question
Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?
answer
random collisions, chemical attractions, and receptor specificity
question
The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?
answer
entry and release
question
The phenomenon of transduction is associated with which of the stages of a bacteriophage infection cycle?
answer
assembly
question
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but not in the lysogenic cycle?
answer
digestion of host DNA
question
Why is lysogeny advantageous to a bacteriophage?
answer
the genetic material of the bacteriophage can be passed on to future generations of cells.
question
Which of the following agents is capable of inducing conversion of a prophage back to a lytic phage?
answer
UV light and X rays
question
Viruses are shed slowly and steadily during
answer
persistent infection
question
During _________, viruses remain dormant in a cell.
answer
latency
question
Virus replication results in the death of the cell in a(n) ________ infection.
answer
lytic
question
_________is a mechanism of release for enveloped viruses.
answer
budding
question
Which of the following would be an appropriate mode of action for a new anticancer drug?
answer
inactivation of an oncogene
question
Both viruses and carcinogenic chemicals can cause tumors by
answer
disrupting cell division controls.
question
Viruses cause most human cancers. T or F
answer
F
question
________, genes that play a role in proper cell division, may also play a role in some types of cancer.
answer
Protooncogenes
question
Tumors invade other organs and tissues in a process called
answer
metastasis.
question
Virus infection results in cancer in the process of
answer
oncogenesis
question
A(n) ________ is a clear zone on a bacterial lawn where cells have been killed by the activity of a bacteriophage.
answer
plaque
question
Zones of clearing in cell cultures that are the result of virus infection are called plaques. Sometimes "cloudy plaques" are seen on bacterial cultures infected with bacteriophage. What type of viral infection might cause this appearance?
answer
lysogenic
question
The normal function of the PrP protein in mammals is believed to be:
answer
assisting in normal synaptic development and function.
question
How do normal prion proteins (PrP) differ from the infectious prion proteins?
answer
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
question
How does the number of infectious prions increase?
answer
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
question
Why are the beta-pleated multimers of PrP potentially pathogenic?
answer
The multimers are more stable and resistant to protease.
question
Which of the following prion diseases is found in deer and elk?
answer
Chronic wasting disease
question
Which of the following prion diseases was also known as laughing disease?
answer
Kuru
question
Which of the following conditions in humans is linked to bovine spongiform encephalopathy?
answer
Variant Creutzfeldt-Jakob disease
question
What part of the nervous system is most affected by fatal familial insomnia?
answer
Thalamus
question
Where does the name "scrapie" come from?
answer
The prion disorder causes infected sheep to scrape against objects until their skin is raw.
question
From which phrase is the term "prions" derived?
answer
Proteinaceous infectious particles
question
In what year did Stanley Prusiner discover prions?
answer
1982
question
Which disease did Stanley Prusiner first identify as being caused by prions?
answer
Scrapie
question
How are prions different from other infectious agents?
answer
They lack nucleic acid.
question
Which of the following diseases is NOT caused by prions?
answer
Hodgkin's lymphoma
question
Many diseases of plants are caused by infectious RNA molecules lacking capsids. T or F
answer
T
question
Which of the following infectious particles do not have protein in their structure?
answer
viroids
question
Prions are composed of a single protein called ________.
answer
PrP
question
How are prions different from all other known infectious agents?
answer
they lack nucleic acid.
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New