How can we help?

You can also find more resources in our Help Center.

76 terms

Microbiology Test II ch13

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