ch 13

The genome of which of the following types of animal virus can act directly as mRNA? ssDNA viruses dsRNA viruses -ssRNA viruses retroviruses +ssRNA viruses

+ssRNA viruses

In what year did Stanley Prusiner discover prions? 1997 1979 1982 1928

1982

In a plaque assay, a microbiologist counts 20 plaques on a plate. 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? 2 10 20 40

20

Put the following viral structures in order, from simplest to most complex: I. virion II. capsomere III. capsid IV. nucleocapsid I, II, IV, III II, III, IV, I II, IV, III, I III, II, I, IV

II, III, IV, I

Which of the following lists stages of a lytic replication cycle in order, from earliest to latest stages? I. Synthesis II. Assembly III. Attachment IV. Release V. Entry

III, V, I, II, IV

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.

Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.

How does the number of infectious prions increase? Prions reproduce by binary fission. Prions form multimers which can then form more single copies of the prion protein. Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion. Prions reproduce by mitosis.

Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.

From which phrase is the term "prions" derived? Protein infections Particles of infection Protein infection of the nervous system Proteinaceous infectious particles

Proteinaceous infectious particles

Why are the beta-pleated multimers of PrP potentially pathogenic? They are found on the surface of immune cells, resulting in damage to the immune system. The multimers are more stable and resistant to protease. They repress the immune system. They are not detected by other organisms.

The multimers are more stable and resistant to protease.

What factor may induce a prophage to enter the lytic cycle? Infection by an additional phage replication of the host bacterium burst time UV light

UV light

Virus replication results in the death of the cell in ________ infection(s). a latent a persistent a lysogenic a lytic both latent and persistent

a lytic

Lysogenic viral DNA which has integrated into the host genome is referred to as

a prophage

Contact between a phage and its bacterial host occurs by _____. a random collision using phage tail fibers using jet-style propulsion using flagella

a random collision

In which stage does formation of mature viruses occur? Penetration Attachment Release Assembly Biosynthesis

assembly

The normal function of the PrP protein in mammals is believed to be: assisting in normal synaptic development and function. assisting proteins in forming beta-pleated sheets. assisting proteins in forming alpha-helices. assisting in normal membrane development and function.

assisting in normal synaptic development and function.

A(n) ________ is a virus that infects bacterial cells. .bacteriophage prion envelope nucleocapsid virion

bacteriophage

The host DNA is usually degraded during which stage? Release Penetration Biosynthesis Attachment Assembly

biosynthesis

The process known as ________ is a mechanism of release for enveloped viruses. metastasis budding persistent infection latency lytic replication

budding

Which of the following is an essential component of all viruses? ribosomes envelope capsid DNA

capsid

Viral capsids are composed of subunits called (capsomeres/nucleocapsids/prions).

capsomeres

What is the typical incubation period for prion diseases? 2-3 weeks 6-12 months decades 3-5 days

decades

Plaque assays are used for counting the number of latent phages in a cell. cultivating viruses that cannot be grown any other way. evaluating the cancer-causing ability of a virus. determining the density of phage in a culture. the study of prions.

determining the density of phage in a culture

Replication of most ________ viruses is similar to normal cellular processes. dsRNA -ssRNA dsDNA +ssRNA ssDNA

dsDNA

Which of the following events might trigger induction of a temperate bacteriophage? Normal cell division of an infected cell An infected cell entering the logarithmic phase of growth Bacterial conjugation Exposure to UV light

exposure to UV light

Bacteriophage release is a gradual process in which small numbers are released at a time. t or f

false

Which of the following would be an appropriate mode of action for a new anticancer drug? inactivation of an oncogene activation of an oncogene inactivation of a repressor activation of a protooncogene

inactivation of an oncogene

In _________, a phage is excised from the host chromosome via physical or chemical agents that damage the genetic material of the host.

induction

Host specificity of a virus is due to oparticular genes that it shares with the infected cell. the presence of an envelope. the presence or absence of a cell wall on the host cell. differences in size between the virus and the host cell. interactions between viral and cellular surface molecules.

interactions between viral and cellular surface molecules.

What is the fate of the prophage during the lysogenic stage? It is degraded by the activity of host defense enzymes. It is copied every time the host DNA replicates. 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.

it is copied every time the host DNA replicates

During the lysogenic cycle, it is possible for integrated phage genes to change the characteristics of the host cell. This is known as _____. synthesis induction transduction lysogenic conversion

lysogenic conversion

when the phenotype of a bacterium is change via ____________, harmless bacteria can become pathogenic and are able to produce deadly toxins an proteins

lysogenic conversion

When a bacteriophage infects hosts' cells and allows them to grow and replicate normally for many generations before lysis, this is considered ____________

lysogeny

The combination of a virus's protein coat and nucleic acid core is called the (capsid/virion/nucleocapsid).

nucleocapsid

Double-stranded RNA genomes can be found in both cells and viruses. only in prions. only in cells. only in viruses. in both prions and viruses.

only in viruses

What portion of bacteriophage T4 enters E. coli? The entire phage enters into the bacterial cell. Only the tail fibers penetrate into the interior of the bacterial cell. No portion of phage T4 actually enters the bacterial cell. Only the T4 genome enters the bacterial cell.

only the T4 genome enters the bacterial cell

In which stage is the viral DNA introduced into the cell? Biosynthesis Assembly Attachment Release Penetration

penetration

During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules? A phage traps the host DNA in an endosome. The phage integrates its DNA into the host cell DNA. The host DNA is released from the cell. Phage enzymes degrade the bacterial DNA.

phage enzymes degrade the bacterial DNA

Viroids infect fungi. plants. plants and animals. bacteria. all organisms.

plants

A (colony/plaque/prophage) is a clear zone on a bacterial lawn where cells have been killed by the activity of a bacteriophage.

plaque

Which of the following is a feature shared by viruses and living organisms? metabolic capability possession of a genome that directs synthesis of materials necessary for replication responsiveness the ability to increase in size presence of cytoplasm

possession of a genome that directs synthesis of materials necessary for replication

A(n) ________ is a bacterial virus which is integrated into the host cell DNA. .lytic phage plasmid prophage insertion phage transposon

prophage

An inactive bacteriophage is a ________ that can remain in the host chromosome and render the bacterium resistant to additional infection by other similar viruses.

prophage

prion

protein particles that cause disease

Reverse transcriptase is associated with which of the following? +ssRNA viruses retroviruses dsDNA viruses -ssRNA viruses dsRNA viruses

retroviruses

Which disease did Stanley Prusiner first identify as being caused by prions? Scrapie Mad cow disease Fatal familial insomnia Kuru

scrapie

Some viruses have a dsDNA genome. Others may have a ________ genome. .dsRNA ssRNA ssDNA ssRNA or dsRNA ssDNA, ssRNA, or dsRNA

ssDNA, ssRNA, or dsRNA

Viruses can be grown in all of the following EXCEPT __________. live animalse mbryonated eggs sterile nutrient agar tissue culture

sterile nutrient agar

Once entry into the bacterial cell has been achieved, the next step in a lytic replication cycle is _____. .assembly release synthesis attachment

synthesis

_____________ is another name for lysogenic phages that have a lysogenic replication cycle.

temperate phages

In a lytic cycle of replication, release of phages involves _____. contact with another uninfected bacterium keeping the host cell alive exocytosis of phages across the cell wall the bacterial cell bursting open

the bacterial cell bursting open

Why is lysogeny advantageous to a bacteriophage? it speeds up the viral infection cycle. it allows the bacteriophage to destroy the host cell's DNA. it enables the bacteriophage to take over the cell. it allows the bacteriophage to infect cells it would not normally infect. the genetic material of the bacteriophage is amplified many times over that seen in a lytic phage.

the genetic material of the bacteriophage is amplified many times over that seen in a lytic phage.

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell? The host cell is allowed to live during the lytic stage. The host cell dies during the lytic stage. The viral DNA may integrate into the host genome during the lytic stage. The host cell can only divide during the lytic stage.

the host cell dies during the lytic stage

A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____. the bacterial cell is broken open, destroying the cell the host DNA is degraded attachment of the phage involves a random collision the phage genome inserts itself into the host genome

the phage genome inserts itself into the host genome

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 cell could still be revived by the virus. The virus would not be able to infect new hosts.

the virus would not be able to infect new hosts

Conventional genetic analyses of prions involving rRNA sequences are impossible because __________. they cannot be isolated in a pure form they contain DNA, but not rRNA they are too small to be analyzed genetically they do not contain nucleic acids

they do not contain nucleic acids

How are prions different from other infectious agents? They lack protein. They cannot replicate. They cause cardiovascular disease. They lack nucleic acid.

they lack nucleic acid

Which of the following is NOT a way in which viruses differ from all other living things? They do not grow. They live inside host cells. They cannot self-replicate. They cannot respond to environmental stimuli through metabolic changes.

they live inside host cells

RNA viruses such as HIV require the activity of reverse (polymerase/transcriptase/transposase) to become proviruses.

transcriptase

Bovine spongiform encephalopathy is an example of a prion disease. t or f

true

Members of a virus family have the same type of nucleic acid. t or f

true

Which of the following is a characteristic by which viruses are classified? type of life cycle size type of nucleic acid type of host number of chromosomes

type of nucleic acid

Small circular RNAs called ________ are plant pathogens. prions viruses viroids phages plasmids

viroids

In what ways do viruses differ from other pathogens? Viruses are composed of both protein and lipid. Viruses lack cytoplasm and organelles. Viruses have no protein structure. Viruses are composed of protein only. Viruses lack genetic material.

viruses lack cytoplasm and organelles