Combo with Chapter 13 Mastering Micro HW and 2 others – Flashcards
Unlock all answers in this set
Unlock answersquestion
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
Lysogenic viral DNA integrating into the host genome is referred to as
answer
prophage
question
Which of the following events might trigger induction of a temperate bacteriophage? ANSWER: 1) Normal cell division of an infected cell 2) Bacterial conjugation 3) An infected cell entering the logarithmic phase of growth 4) Exposure to UV light
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 cell dies during the lytic stage.
question
What is the fate of the prophage during the lysogenic stage? 1) It is packaged into viral proteins and maintained until the host is exposed to an environmental stress. 2) It is copied every time the host DNA replicates. 3) It is degraded by the activity of host defense enzymes. 4) It is released from the cell by lysing the cell.
answer
It is copied every time the host DNA replicates.
question
How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
answer
Their nucleic acids are injected into the cell.
question
Which virus employs the use of an RNA-dependent RNA polymerase?
answer
+RNA viruses
question
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
answer
retroviruses
question
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane? +RNA viruses dsRNA viruses Naked viruses Enveloped viruses
answer
enveloped viruses
question
Which of the following can be used directly as messenger RNA? +RNA -RNA ssDNA
answer
+RNA
question
Which of the following statements concerning prion diseases is true? Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc). Prion diseases are always inherited. Prion diseases affect humans but not other animals. Prion diseases affect brain function but do not affect the morphology (overall appearance) of brain tissues.
answer
Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).
question
Which of the following statements concerning viruses is true? Viruses contain both DNA and RNA, and they undergo binary fusion. Viruses possess enzymes for protein synthesis and ATP generation. The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach. Viruses are usually about the same size as bacteria.
answer
The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
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/maturation
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? The virus would infect new hosts. The virus would not be able to infect new hosts. The cell could still be revived by the virus.
answer
The virus would not be able to infect new hosts.
question
Name the human disease caused by prions?
answer
Creutzfeldt-Jakob disease (CJD)
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
Which of the following statements regarding latent viral infections is true? During latent infections, small amounts of virus are produced, and virus numbers build up over time. Latent infections can persist for years in an individual without causing any symptoms. Latent viral infections are caused by the slow conversion of cellular glycoproteins from normal to infectious form. Latent viral infections are almost always fatal.
answer
Latent infections can persist for years in an individual without causing any symptoms.
question
Which statement is CORRECT concerning animal viruses? The genome of animal viruses is always single-stranded. Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA. Capsid proteins are produced in the nucleus. Enveloped viruses are surrounded by a lipid and carbohydrate coat, which is made from the host cell's mitochondria.
answer
Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA.
question
Which of the following is true concerning a lysogenic viral replication cycle? ANSWER: Lysogenic infections are similar to persistent infections, in that virus is constantly produced. During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome. During lysogeny, the viral DNA is present as a circular plasmid. Once the lysogenic portion of the cycle has begun, virus is never produced again.
answer
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
question
Which virus is NOT associated with cancer? ANSWER: Epstein-Barr virus (EBV) coronavirus human papillomavirus (HPV) hepatitis B virus (HBV)
answer
coronavirus
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 pathog
answer
The multimers are more stable and resistant to protease.
question
protection and recognition
answer
The outermost layer of a virion fulfills what functions of the virus?
question
nucleic acid
answer
During the intracellular state, a virus exists as
question
type of nucleic acid
answer
Viruses are primarily classified according to their
question
interactions
answer
Host specificity of a virus is due to
question
envelope
answer
What would NOT be found as a component of a bacteriophage?
question
in both cells and viruses
answer
A lipid membrane is present
question
both cells and viruses
answer
Double-stranded DNA genomes are found in
question
cells only
answer
Cytoplasm is a characteristic of
question
true
answer
Most viruses cannot be seen by light microscopy. TRUE OR FALSE
question
true
answer
Protozoa are susceptible to viral attack. TRUE OR FALSE
question
they require a host to reproduce
answer
How are viruses different from cells?
question
package and protect the viral genome
answer
What is the function of the structural elements of a virus?
question
a prophage
answer
Lysogenic viral DNA integrating into the host genome is referred to as
question
exposure to UV light
answer
what event might trigger induction of a temperate bacteriophage?
question
host cell dies during lytic stage
answer
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
question
copied every time the host DNA replicates
answer
What is the fate of the prophage during the lysogenic stage?
question
penetration
answer
In which stage is the viral DNA introduced into the cell?
question
assembly
answer
In which stage does formation of mature viruses occur?
question
biosynthesis
answer
The host DNA is usually degraded during which stage?
question
virus would not infect the new host
answer
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
question
lysogenic conversion
answer
Bacteriophage genes that cause toxin production in a normally harmless bacterial species are an example of _____.
question
the infected cell may live for a long time
answer
Infections with enveloped animal viruses are similar to lysogenic phage infections because _____.
question
entry and release
answer
Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4?
question
UV light and X rays
answer
What agent is capable of inducing conversion of a prophage back to a lytic phage?
question
prusiner
answer
Which of the following individuals discovered prions?
question
virion
answer
what is a virus in the extracellular state?
question
plant
answer
The first virus to be identified was isolated from a _____.
question
protein
answer
The capsid of a virus is made out of which of the following types of molecules?
question
prion
answer
does NOT refer to viral shapes
question
dependent on host cell
answer
Why do viruses have to infect host cells?
question
attachment
answer
The tail fibers of a bacteriophage are most useful during which of the following stages of the lytic replication cycle?
question
viral DNA
answer
Which of the following is a major difference between a lysogenic and a lytic cycle in bacteriophages?
question
retroviruses
answer
What viruse creates a DNA intermediary molecule from the information in their RNA genomes?
question
herpesviruses
answer
What types of viruse replicates in the cell's nucleus?
question
rna dependent
answer
What type of viruses replicates in the cell's nucleus?
question
cytoplasmic membrane
answer
Bacteriophages can use all of the following structures for attachment to a bacterial cell EXCEPT _____.
question
envelope
answer
A naked virus is one without _____.
question
uncoating
answer
Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.
question
phage persists
answer
Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.
question
cancer causing viruses
answer
In the early 1900s, the virologist F. Peyton Rous discovered _____.
question
allow bacteriophages to become latent
answer
Fertilized chicken eggs are useful for the culture of viruses for all of the following reasons EXCEPT _____.
question
continuous
answer
HeLa cells are an example of a __________ cell culture.
question
contain no nucleic acid
answer
Scientists have determined that prion diseases are not caused by a type of slow virus because prions _____.
question
true
answer
Viruses have genomes of DNA or RNA, but never both. TRUE OR FALSE
question
true
answer
Viruses can specifically infect one type of cell within an organism. TRUE OR FALSE
question
true
answer
Bacteriophages outnumber all known life forms. TRUE OR FALSE
question
false
answer
According to the ICTV scheme of classification, viruses can be classified by a variety of characteristics, including the diseases they cause. TRUE OR FALSE
question
true
answer
Proviruses become a permanent part of the host cell's genome. TRUE OR FALSE
question
true
answer
Bacteriophages can be used in place of antibiotics to treat certain bacterial diseases. TRUE OR FALSE
question
true
answer
Lysogenic bacteriophages can be excised from the chromosome by any agent that damages the cell's DNA. TRUE OR FALSE
question
false
answer
Retroviruses need RNA-dependent RNA transcriptase to replicate themselves. TRUE OR FALSE
question
false
answer
Diploid cell cultures have an unlimited life span. TRUE OR FALSE
question
false
answer
The destruction of chickens and other domesticated fowl prevents the spread of avian influenza. TRUE OR FALSE
question
false
answer
An infection in which a host cell sheds new viruses slowly and steadily is called a latent infection. TRUE OR FALSE
question
spongiform encephalopathies
answer
As a group, prion diseases are more formally known as _____.
question
true
answer
An icosahedral capsid is the most common type of polyhedral capsid and is also found in bacteriophage. TRUE OR FALSE
question
viroids
answer
Small, circular RNA molecules that are infectious to plants are called _____.
question
false
answer
Viruses are classified into kingdoms and divisions, just like bacteria and eukaryotes.
question
induction
answer
A prophage is excised from the host chromosome and viral replication proceeds in a process called _____.
question
false
answer
The viral envelope contains phospholipids and proteins, all of which originate from the host membrane.
question
assembly
answer
Which step in the viral life cycle is usually a spontaneous process, but is sometimes controlled by viral enzymes?
question
false
answer
If neoplasia occurs, this means that cancer will follow. TRUE OR FALSE
question
host membrane merges
answer
What is the main difference between membrane fusion and endocytosis?
question
Which of the following statements concerning viruses is true?
answer
The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
question
Which statement concerning viral structure is true?
answer
Spikes are found on some viruses. They are very consistent in structure and can be used for identification.
question
How does specialized transduction differ from regular lysogeny?
answer
The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.
question
What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?
answer
The host DNA integrates, with the prophage, into the new recipient chromosome.
question
How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?
answer
The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
question
Which of the following is true concerning a lysogenic viral replication cycle?
answer
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
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
How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
answer
Their nucleic acids are injected into the cell.
question
Which virus employs the use of an RNA-dependent RNA polymerase?
answer
+RNA viruses
question
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
answer
Retroviruses
question
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane?
answer
Enveloped viruses
question
Which of the following can be used directly as messenger RNA?
answer
+RNA
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
Which of the following statements regarding latent viral infections is true?
answer
Latent infections can persist for years in an individual without causing any symptoms.
question
Which of the following is true regarding cultivation and isolation of animal viruses?
answer
Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host.
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
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 statements concerning prion diseases is true?
answer
Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).
question
Which of the following is true of viroids?
answer
Viroids are short pieces of naked RNA.
question
How do all viruses differ from bacteria?
answer
Viruses are not composed of cells.
question
Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals?
answer
They cannot reproduce themselves outside a host.
question
Which of the following statements about viruses is FALSE?
answer
Viruses use their own catabolic enzymes.
question
Which of the following statements about viral spikes is FALSE?
answer
They are found only on nonenveloped viruses.
question
Which of the following is NOT used as a criterion to classify viruses?
answer
biochemical tests
question
What contributes to antigenic shift in influenza viruses?
answer
a segmented genome
question
A viral species is a group of viruses that
answer
has the same genetic information and ecological niche.
question
Viruses that utilize reverse transcriptase belong to the virus families
answer
Hepadnaviridae and Retroviridae.
question
DNA made from an RNA template will be incorporated into the virus capsid of
answer
Hepadnaviridae.
question
Which of the following is NOT utilized to culture viruses?
answer
culture media
question
A clear area against a confluent "lawn" of bacteria is called a
answer
plaque
question
Continuous cell lines differ from primary cell lines in that
answer
continuous cell lines can be maintained through an indefinite number of generations.
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 cell 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
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
Bacteriophages and animal viruses do NOT differ significantly in which one of the following steps?
answer
biosynthesis
question
The definition of lysogeny is
answer
phage DNA is incorporated into host cell DNA.
question
Which of the following statements is FALSE?
answer
The prophage makes the host cell immune to infection by other phages.
question
Lysogeny can result in all of the following EXCEPT
answer
immunity to reinfection by any phage.
question
Which of the following would be the first step in biosynthesis of a virus with a - (minus) strand of RNA?
answer
synthesis of double-stranded RNA from an RNA template
question
An envelope is acquired during which of the following steps?
answer
release
question
A viruss ability to infect an animal cell depends primarily upon the
answer
presence of receptor sites on the cell membrane.
question
Assume you have isolated an unknown virus. This virus has a single, positive sense strand of RNA, and possesses an envelope. To which group does it most likely belong?
answer
togavirus
question
The mechanism whereby an enveloped virus leaves a host cell is called
answer
budding
question
Bacteriophages derive all of the following from the host cell EXCEPT
answer
lysozyme
question
Bacteriophage replication differs from animal virus replication because only bacteriophage replication involves
answer
injection of naked nucleic acid into the host cell.
question
Generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following EXCEPT
answer
DNA polymerase.
question
Which of the following places these items in the correct order for DNA-virus replication? 1. Maturation 2. DNA synthesis 3. Transcription 4. Translation
answer
2; 3; 4; 1
question
The following steps occur during multiplication of herpesviruses. Which is the third step?
answer
uncoating
question
The following steps occur during multiplication of retroviruses. Which is the fourth step?
answer
synthesis of double-stranded DNA
question
Which one of the following steps does NOT occur during multiplication of a picornavirus?
answer
synthesis of DNA
question
Most RNA viruses carry which of the following enzymes?
answer
RNA-dependent RNA polymerase
question
T/F The basic mechanism of viral multiplication is similar for all viruses.
answer
True
question
The most conclusive evidence that viruses cause cancers is provided by
answer
cancer following injection of cell-free filtrates.
question
Oncogenic viruses
answer
cause tumors to develop.
question
An example of a latent viral infection is
answer
cold sores.
question
A lytic virus has infected a patient. Which of the following would best describe what is happening inside the patient?
answer
The virus is causing the death of the infected cells in the patient.
question
Some viruses, such as human herpesvirus 1, infect a cell without causing symptoms. These are called
answer
latent viruses.
question
Assume a patient had chickenpox (human herpesvirus 3) as a child. Which line on the graph in the figure would show the number of viruses present in this person as a 60-year-old with shingles (human herpesvirus 3)?
answer
e
question
Assume a patient has influenza. During which time on the graph in the figure would the patient show the symptoms of the illness?
answer
c
question
A persistent infection is one in which
answer
the disease process occurs gradually over a long period.
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
Which of the following is necessary for replication of a prion?
answer
PrPSc
question
An infectious protein is a
answer
prion
question
A viroid is a(n)
answer
infectious piece of RNA without a capsid.
