Chapter 13 – Mastering Microbiology

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Which of the following statements describes a generalist virus?

It infects many kinds of cells in many different hosts

All of these are steps in the lytic cycle of a temperate bacteriophage. Which happens second?

1. attachment *2. ENTRY 3. bacterial chromosome degraded 4. synthesis 5. assembly 6. release

Which of the following is NOT represented in viral classification schemes?

1. order 2. family 3. genus 4. specific epithet *class is NOT

Which of the following diseases is NOT caused by prions?

1. Bovine Spongiform Encephalitis 2. Kuru 3. Scrapie *Chagas’ disease is NOT

Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4?

Entry and Release

Conventional genetic analyses of prions involving rRNA sequences are impossible because __________.

they do not contain nucleic acids

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 (such as endocytosis or active transport)

Which of the following is an essential component of all viruses?

a. ribosomes *b. capsid- all viruses have a capsid surrounding their nucleic acid c. envelope d. DNA

Lysogeny refers to…?

viral DNA becoming imbedded within the host cell’s chromosomes.

Lysogeny is associated with all of the following EXCEPT…
a. bacteriophages
b. animal viruses
c. increasing virulence of host bacterium
d. a prophage

Animal viruses do not undergo lysogeny.

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

capsomere capsid nucleocapsid virion

Viruses can be grown in all of the following EXCEPT __________.
a. embryonated eggs
b. tissue culture
c. sterile nutrient agar
d. live animals

sterile nutrient agar- Viruses cannot be grown in sterile nutrient agar or other microbiological media because viruses must have a host cell present to reproduce.

You have isolated bacterium that contains a prophage. Which of the following is true concerning the prophage?

The phage is in the lysogenic cycle

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?

20. Each plaque on the plate corresponds to a single phage.

Which of the following would be an appropriate mode of action for a new anticancer drug?

inactivation of an oncogene

Which of the following types of enzymes is necessary for the replication of most double-stranded DNA (dsDNA) viruses?

cellular DNA polymerase. Most dsDNA viruses do not require any kind of special enzyme for their replication because they are able to utilize the normal enzymes and processes of the host cell.

Most viral genomes are much smaller than the genomes of the cells they infect. Which of the following CANNOT be inferred from this statement?
a. Viral genomes can be enclosed in very small capsids.
b. Most viruses can infect only certain types of cells.
c. Viral genomes usually contain fewer genes than cellular genomes.
d. Viral genomes usually do not encode all of the enzymes or structures necessary for their replication.

b. Most viruses can infect only certain types of cells.

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

b. they live inside host cells

A phage T4 particle that has lost its tail fibers will have a replication cycle that is blocked at which of the following stages?
a. entry
b. synthesis
c. attachment
d. assembly


Both viruses and carcinogenic chemicals can cause tumors by __________.

a. killing cells
b. disruption of cell division
c. creating new cellular genes
d. slowing cellular growth

disruption of cell division

Contact between a phage and its bacterial host occurs by _____.

a random collision

What portion of bacteriophage T4 enters E. coli?

Only the T4 genome enters the bacterial cell.

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

Only the T4 genome enters the bacterial cell.

During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules?

Phage enzymes degrade the bacterial DNA.

In a lytic cycle of replication, release of phages involves _____.

the bacterial cell bursting open

A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____.

the phage genome inserts itself into the host genome

What factor may induce a prophage to enter the lytic cycle?

UV light

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

lysogenic conversion

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

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

a prophage

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

exposure to UV light

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

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

it is copied every time the host DNA replicates

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?


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?


What occurs during viral uncoating?

the capsid breaks apart

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

assisting the normal synaptic development and function

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

normal PrP have alpha-helicases; infectious PrP have beta-pleated sheets

How does the number of infectious prions increase?

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

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

The multimers are more stable and resistant to protease

From which phrase is the term "prions" derived?

Proteinaceous infectious particles

How are prions different from other infectious agents?

they lack nucleic acid

The infectious cycles of enveloped animal viruses and temperate bacteriophages are most similar because __________.

the infected cell may live for a long time. Because enveloped viruses are shed slowly and persistently from the host cell by budding, the host cell may survive for a long time.

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