***Microbiology Chapter 13***

Which of the following prion diseases is found in deer and elk?

Chronic wasting disease

Which of the following is true regarding cultivation and isolation of animal viruses?

Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host.

Which of the following is true concerning a lysogenic viral replication cycle?

During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.

Where does the name "scrapie" come from?

The prion disorder causes infected sheep to scrape against objects until their skin is raw.

How does specialized transduction differ from regular lysogeny?

The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.

How are prions different from other infectious agents?

They lack nucleic acid.

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

T/F The basic mechanism of viral multiplication is similar for all viruses.

True

Viruses that utilize reverse transcriptase belong to the virus families

Hepadnaviridae and Retroviridae.

DNA made from an RNA template will be incorporated into the virus capsid of

Hepadnaviridae.

What is the fate of the prophage during the lysogenic stage?

It is copied every time the host DNA replicates.

The normal function of the PrP protein in mammals is believed to be:

assisting in normal synaptic development and function.

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

Which of the following prion diseases was also known as laughing disease?

Kuru

Which of the following statements regarding latent viral infections is true?

Latent infections can persist for years in an individual without causing any symptoms.

How do normal prion proteins (PrP) differ from the infectious prion proteins?

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

From which phrase is the term "prions" derived?

Proteinaceous infectious particles

Most RNA viruses carry which of the following enzymes?

RNA-dependent RNA polymerase

Which statement concerning viral structure is true?

Spikes are found on some viruses. They are very consistent in structure and can be used for identification.

What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?

The host DNA integrates, with the prophage, into the new recipient chromosome.

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

The host cell dies during the lytic stage.

Why are the beta-pleated multimers of PrP potentially pathogenic?

The multimers are more stable and resistant to protease.

In what year did Stanley Prusiner discover prions?

1982

Which of the following can be used directly as messenger RNA?

+RNA

Which virus employs the use of an RNA-dependent RNA polymerase?

+RNA viruses

Which of the following places these items in the correct order for DNA-virus replication? 1. Maturation 2. DNA synthesis 3. Transcription 4. Translation

2; 3; 4; 1

The most conclusive evidence that viruses cause cancers is provided by

cancer following injection of cell-free filtrates.

Oncogenic viruses

cause tumors to develop.

An example of a latent viral infection is

cold sores.

Continuous cell lines differ from primary cell lines in that

continuous cell lines can be maintained through an indefinite number of generations.

Which of the following is NOT utilized to culture viruses?

culture media

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)?

e

A viral species is a group of viruses that

has the same genetic information and ecological niche.

Lysogeny can result in all of the following EXCEPT

immunity to reinfection by any phage.

A viroid is a(n)

infectious piece of RNA without a capsid.

Bacteriophage replication differs from animal virus replication because only bacteriophage replication involves

injection of naked nucleic acid into the host cell.

Some viruses, such as human herpesvirus 1, infect a cell without causing symptoms. These are called

latent viruses.

Bacteriophages derive all of the following from the host cell EXCEPT

lysozyme

The definition of lysogeny is

phage DNA is incorporated into host cell DNA.

A clear area against a confluent "lawn" of bacteria is called a

plaque

A viruss ability to infect an animal cell depends primarily upon the

presence of receptor sites on the cell membrane.

An infectious protein is a

prion

An envelope is acquired during which of the following steps?

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?

release

Which one of the following steps does NOT occur during multiplication of a picornavirus?

synthesis of DNA

The following steps occur during multiplication of retroviruses. Which is the fourth step?

synthesis of double-stranded DNA

Which of the following would be the first step in biosynthesis of a virus with a - (minus) strand of RNA?

synthesis of double-stranded RNA from an RNA template

A persistent infection is one in which

the disease process occurs gradually over a long period.

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?

togavirus

The following steps occur during multiplication of herpesviruses. Which is the third step?

uncoating

In which stage does formation of mature viruses occur?

Assembly

The host DNA is usually degraded during which stage?

Biosynthesis

Generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following EXCEPT

DNA polymerase.

Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane?

Enveloped viruses

Which of the following events might trigger induction of a temperate bacteriophage?

Exposure to UV light

Which of the following statements concerning prion diseases is true?

Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).

In which stage is the viral DNA introduced into the cell?

Penetration

Which of the following is necessary for replication of a prion?

PrPSc

How does the number of infectious prions increase?

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

Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?

Retroviruses

Which disease did Stanley Prusiner first identify as being caused by prions?

Scrapie

What part of the nervous system is most affected by fatal familial insomnia?

Thalamus

Which of the following statements concerning viruses is true?

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.

What occurs during viral uncoating?

The capsid breaks apart, releasing the viral genome.

Which of the following statements is FALSE?

The prophage makes the host cell immune to infection by other phages.

How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?

The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.

A lytic virus has infected a patient. Which of the following would best describe what is happening inside the patient?

The virus is causing the death of the infected cells in the patient.

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.

How do naked viruses differ from enveloped viruses in their attachment/penetration phase?

Their nucleic acids are injected into the cell.

Which of the following statements about viral spikes is FALSE?

They are found only on nonenveloped viruses.

Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals?

They cannot reproduce themselves outside a host.

Which of the following conditions in humans is linked to bovine spongiform encephalopathy?

Variant Creutzfeldt-Jakob disease

Which of the following is true of viroids?

Viroids are short pieces of naked RNA.

How do all viruses differ from bacteria?

Viruses are not composed of cells.

Which of the following statements about viruses is FALSE?

Viruses use their own catabolic enzymes.

Lysogenic viral DNA integrating into the host genome is referred to as

a prophage.

What contributes to antigenic shift in influenza viruses?

a segmented genome

Which of the following is NOT used as a criterion to classify viruses?

biochemical tests

Bacteriophages and animal viruses do NOT differ significantly in which one of the following steps?

biosynthesis

The mechanism whereby an enveloped virus leaves a host cell is called

budding

Assume a patient has influenza. During which time on the graph in the figure would the patient show the symptoms of the illness?

c