Chapter 13
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.
b. The virus would not be able to infect new hosts.
What is the most likely etiology (cause) of this disease? bacterium fungus virus prion
d. prion
Viruses can be grown in all of the following EXCEPT __________. tissue culture live animals embryonated eggs sterile nutrient agar
d. sterile nutrient agar
A(n) ________ is a virus that infects bacterial cells. virion nucleocapsid prion envelope bacteriophage
e. bacteriophage
What is the function of the structural elements of a virus? To provide a source of energy for the virus To package and protect the viral genome To use all of the cell proteins
b. To package and protect the viral genome
Which of the following infectious particles is most susceptible to damage a. naked capsid virus b. enveloped virus c. prions d. bacteriophage e. both naked capsid viruses and prions
b. enveloped virus
Students identified RSV and influenza as possible causes of Uncle Luis' lung infection. In terms of characteristics used to classify viruses, what distinguishes these two viruses? Genome composition Presence/absence of an envelope Genome structure Host cell
c. Genome structure
How are viruses different from eukaryotic cells? They do not contain enzymes. They do not contain genetic material. They require a host in order to reproduce. They do not contain protein.
c. They require a host in order to reproduce.
Naked capsid animal viruses are commonly released from the infected cell by ________, a process the host cell does not survive. endocytosis exocytosis lysis membrane fusion budding
c. lysis
How do normal prion proteins (PrP) differ from the infectious prion proteins? Normal PrP are found in all mammals; infectious PrP are found in only cows. Normal PrP are found on mammals; infectious PrP are found on reptiles. Normal PrP lack nucleic acid; infectious PrP have nucleic acid. Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
d. Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
Which of the following prion diseases was also known as laughing disease? Creutzfeldt-Jakob disease Gerstmann-Straussler-Scheinker syndrome Kuru Bovine spongiform encephalopathy
Kuru
A pathogen that has chitin in its cell wall would also have _________. Ergosterol 70S ribosomes Peptidoglycan Mycolic acids
a. Ergosterol
In which stage does formation of mature viruses occur? Release Assembly Attachment Penetration Biosynthesis
b. Assembly
How are prions different from all other known infectious agents? A) They cannot reproduce outside a cell. B) They act as slow viruses. C) They cause neurological problems. D) They can be destroyed by incineration. E) They lack nucleic acid.
E) They lack nucleic acid.
Which of the following is NOT true about viroids? They are made of ssRNA. They may cause plant stunting. They are small infectious particles. A viroid causes chronic wasting disease in deer and elk.
d. A viroid causes chronic wasting disease in deer and elk.
Which of the following events might trigger induction of a temperate bacteriophage? Bacterial conjugation An infected cell entering the logarithmic phase of growth Normal cell division of an infected cell Exposure to UV light
d. Exposure to UV light
What is a virion? 1. An empty capsid. 2. An extracellular virus genome. 3. A virus genome inside a cell. 4. A virus genome integrated into a host cell genome. 5. A single virus particle outside a cell.
5. A single virus particle outside a cell.
In which stage is the viral DNA introduced into the cell? Penetration Release Biosynthesis Assembly Attachment
A. Penetration
The host DNA is usually degraded during which stage? Biosynthesis Attachment Release Assembly Penetration
a. Biosynthesis
Which of the following diseases is NOT caused by prions? Chagas' disease kuru scrapie bovine spongiform encephalitis
a. Chagas' disease
In what year did Stanley Prusiner discover prions? 1997 1982 1979 1928
b. 1982
How many plaque-forming units can be assumed to have been present in the original bacterium-virus mixture on the plate, if there was no dilution of the mixture prior to plating?
20
How are prions different from other infectious agents? They cannot replicate. They cause cardiovascular disease. They lack protein. They lack nucleic acid.
d. They lack nucleic acid.
Which of the following laboratory procedures is used for culturing animal viruses in the laboratory? A) cell cultures B) both cell cultures and embryonated eggs C) broth cultures D) embryonated eggs E) synthetic cytoplasm
B) both cell cultures and embryonated eggs
How did this man most likely become exposed to this disease agent? He is likely to have been exposed while hunting elk in Colorado during his childhood. He was exposed to this disease while eating exotic foods in Europe. He was exposed to this disease during trans-Atlantic flights to Europe. He was exposed to this disease while hunting in Europe.
a. He is likely to have been exposed while hunting elk in Colorado during his childhood.
Please choose the correct description of the term below that is associated with lysogenic replication.
1. "Temperate phages" is another name for lysogenic phages that have a lysogenic replication cycle. 2. An inactive bacteriophage is a "Prophage" that can remain in the host chromosome and render the bacterium resistant to additional infection by other similar viruses. 3. When the phenotype of a bacterium is changed via "Lysogenic conversion" harmless bacteria can become pathogenic and are able to produce deadly toxins and proteins. 4. In "Induction", a phage is excised from the host chromosome via physical or chemical agents that damage the genetic material of the host. 5. When a bacteriophage infects hosts' cells and allows them to grow and replicate normally for many generations before lysis, this is considered "Lysogeny".
Sort these pathogens based on the most useful/informative characteristics that would allow you to unambiguously identify the pathogen as a source of an infection.
The following can be distinguished by their rRNA sequence: Mycobacterium tuberculosis, Legionella pneumophila, and Coccidioides immitis. The following can be distinguished by their cell wall sructure: Mycobacterium tuberculosis and Coccidioides immitis. The following can be distinguished by their genome structure and composition: Respiratory syncytial virus (RSV) and Influenza virus. The following can be identified using a Gram stain: Legionella pneumophila. Legionella pneumophila returned
What is the fate of the prophage during the lysogenic stage? It is copied every time the host DNA replicates. It is degraded by the activity of host defense enzymes. It is released from the cell by lysing the cell. It is packaged into viral proteins and maintained until the host is exposed to an environmental stress.
a. It is copied every time the host DNA replicates.
Lysogenic viral DNA which has integrated into the host genome is referred to as a prophage. induction. lytic. lysogeny.
a. a prophage.
Which of the following is an essential component of all viruses? capsid ribosomes DNA envelope
a. capsid
Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4? entry and release synthesis attachment assembly
a. entry and release
A drug targets chitin. Which type of pathogen should this drug be effective against? fungi viruses bacteria both bacteria and fungi
a. fungi
Is this disease contagious? Yes, it is likely to be transmitted by ticks in the Rocky Mountains. No, the disease is not contagious. Yes, it is likely to be transmitted by infected mountain streams in the Rocky Mountains. No, this disease is transmitted only by mosquitoes.
b. No, the disease is not contagious.
What is the typical incubation period for prion diseases? 6-12 months 2-3 weeks 3-5 days decades
d. decades
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell? The host cell can only divide during the lytic stage. The host cell dies during the lytic stage. The host cell is allowed to live during the lytic stage. The viral DNA may integrate into the host genome during the lytic stage.
b. The host cell dies during the lytic stage.
The infectious cycles of enveloped animal viruses and temperate bacteriophages are most similar because __________. there is no viral activity, signs, or symptoms of infection in the host cell the viral genome of each always becomes incorporated into the host cell's genome the infected cell may live for a long time virions are released rapidly and in high numbers from lysing cells
c. the infected cell may live for a long time
Which of the following membranes can give rise to a viral envelope? the cytoplasmic membrane the endoplasmic reticulum the nuclear and cytoplasmic membranes and the endoplasmic reticulum the nuclear and cytoplasmic membranes the nuclear membrane
c. the nuclear and cytoplasmic membranes and the endoplasmic reticulum
Which of the following is CORRECT regarding the viral envelope? 1. It is composed of sterols. 2. It contains only viral proteins. 3. It contains only host cell proteins. 4. It is composed of cellular phospholipid membrane, cellular and viral proteins. 5. It is composed of sterols of viral proteins only. It is composed of cellular phospholipid membrane, cellular and viral proteins.
4. It is composed of cellular phospholipid membrane, cellular and viral proteins.
Which of the following infectious particles do NOT have protein in their structure? A) bacteriophages B) prions C) animal viruses D) viroids E) both prions and viroids
D) viroids
A(n) ________ is a bacterial virus which is integrated into the host cell DNA. plasmid insertion phage prophage lytic phage transposon
c. prophage
Which disease did Stanley Prusiner first identify as being caused by prions? Kuru Fatal familial insomnia Scrapie Mad cow disease
c. scrapie
Why are the beta-pleated multimers of PrP potentially pathogenic? They repress the immune system. The multimers are more stable and resistant to protease. They are found on the surface of immune cells, resulting in damage to the immune system. They are not detected by other organisms.
b. The multimers are more stable and resistant to protease.
The process known as ________ is a mechanism of release for enveloped viruses. metastasis budding lytic replication latency persistent infection
b. budding
Which of the following prion diseases is found in deer and elk? Scrapie Bovine spongiform encephalopathy Variant Creutzfeldt-Jakob disease Chronic wasting disease
d. Chronic wasting disease
What part of the nervous system is most affected by fatal familial insomnia? Cerebrum The spinal cord Cerebellum Thalamus
d. Thalamus
Viroids infect fungi. plants and animals. all organisms. bacteria. plants.
e. plants
Why is lysogeny advantageous to a bacteriophage? it enables the bacteriophage to take over the cell. the genetic material of the bacteriophage is amplified many times over that seen in a lytic phage. it speeds up the viral infection cycle. it allows the bacteriophage to destroy the host cell's DNA. it allows the bacteriophage to infect cells it would not normally infect.
b. the genetic material of the bacteriophage is amplified many times over that seen in a lytic phage.
From which phrase is the term "prions" derived? Particles of infection Protein infections Proteinaceous infectious particles Protein infection of the nervous system
c. Proteinaceous infectious particles
Which test confirmed the presence of this prion disease? blood work nutritional deficiency brain scan psychological evaluation
c. brain scan
Both viruses and carcinogenic chemicals can cause tumors by __________. creating new cellular genes disruption of control over the rate of cell division killing cells slowing cellular growth
disruption of control over the rate of cell division
Which of the following is a feature shared by viruses and living organisms? A) presence of cytoplasm B) the ability to increase in size C) responsiveness D) metabolic capability E) possession of a genome that directs synthesis of materials necessary for replication
E) possession of a genome that directs synthesis of materials necessary for replication
Plaque assays are used for A) counting the number of latent phages in a cell. B) the study of prions. C) determine the density of phage in a culture. D) cultivating viruses that cannot be grown any other way. E) evaluating the cancer-causing ability of a virus.
C
Think about the many factors that are used to classify viruses. In order for Lauren to determine the type of virus she may have, she needs to understand some basic concepts about how viruses are characterized. Please sort the following statements as being true or false regarding characteristics of viruses.
Correct Statements *Capsids function to surround & protect the nucleic acid core *The genomes of viruses are usually smaller than the genomes of bacteria *Viruses can have different shapes *The genetic material of a virus can be DNA or RNA *Viruses are not capable of metabolic activity on their own; they must have a host cell to reproduce Incorrect Statements All viruses have both a capsid and an envelope. The intracellular state of a virus is called a virion. Capsids are acquired from the host cell during replication or release.
In what ways do viruses differ from other pathogens? Viruses lack genetic material. Viruses are composed of protein only. Viruses have no protein structure. Viruses are composed of both protein and lipid. Viruses lack cytoplasm and organelles.
e. Viruses lack cytoplasm and organelles.
Which of the following statements describes a generalist virus? It infects many kinds of cells in many different hosts. It does not have a particular sequence of events in its life cycle. It does not cause disease in the organisms it infects. It can have several different types of genomes.
a. It infects many kinds of cells in many different hosts.
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 it is not as dense as a cytoplasmic membrane it is not as flexible as a cytoplasmic membrane it contains different types of phospholipids than does a cytoplasmic membrane
a. it does not perform the physiological functions carried out by the cytoplasmic membrane
Tumors invade other organs and tissues in a process called latency metastasis. budding. neoplasia. uncoating.
b. metastasis.
A person has a suspected lung infection. A sputum sample is Gram stained, but no bacteria are visible. However, bacterial colonies do grow after a prolonged incubation. The patient is successfully treated with an antibiotic regimen that includes isoniazid. Why were no bacteria visible after the initial staining reaction? The bacteria are obligate anaerobes and die upon exposure to oxygen. The bacteria are obligate anaerobes and die upon exposure to oxygen. Mycolic acids in the wall of this pathogen resist uptake of the Gram stain. The bacteria lack a cell wall.
c. Mycolic acids in the wall of this pathogen resist uptake of the Gram stain.
Where does the name "scrapie" come from? The prions cause amyloid plaques to scrape against each other. The disease results in the animal wasting away, sending them to the "scrap heap." The prion disorder causes infected sheep to scrape against objects until their skin is raw.
c. The prion disorder causes infected sheep to scrape against objects until their skin is raw.
The normal function of the PrP protein in mammals is believed to be: assisting proteins in forming alpha-helices. assisting in normal membrane development and function. assisting in normal synaptic development and function. assisting proteins in forming beta-pleated sheets.
c. assisting in normal synaptic development and function.
How does the number of infectious prions increase? Prions form multimers which can then form more single copies of the prion protein. Prions reproduce by mitosis. Prions reproduce by binary fission. Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
d. Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
How is the HIV provirus different from a lambda-phage prophage? Lambda phage-infected cells produce virus slowly over time. All the offspring of a cell infected with a prophage will contain the virus. The HIV provirus is inactive inside the host cell. The HIV provirus is integrated permanently into the host cell's DNA. All subsequent generations of HIV-infected cells carry the provirus.
d. The HIV provirus is integrated permanently into the host cell's DNA.
Which of the following conditions in humans is linked to bovine spongiform encephalopathy? Fatal familial insomnia Gerstmann-Straussler-Scheinker syndrome Kuru Variant Creutzfeldt-Jakob disease
d. Variant Creutzfeldt-Jakob disease
The outermost layer of a virion fulfills which of the following functions of the virus? protection recognition replication both protection and recognition both recognition and replication
d. both protection and recognition
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but NOT in the lysogenic cycle? attachment viral protein synthesis entry digestion of host DNA both digestion of host DNA and viral proteins synthesis
d. digestion of host DNA
