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