chapter 13 Flashcards

Which of the following statements concerning viruses is FALSE?

A) Viruses never contain both DNA and RNA.

B) Viruses enter a cell to complete the replication they have begun extracellularly.

C) Some viruses have an outer membrane called an envelope.

D) Viral capsids can assume one of three basic shapes.

E) Tobacco mosaic virus was the first virus to be discovered and characterized.

The outermost layer of a virion fulfills which of the following functions of the virus?

A) protection

B) recognition

C) replication

D) protection and recognition

E) recognition and replication

During the intracellular state, a virus exists as

A) a lipid.

B) a protein.

C) a nucleic acid.

D) both a protein and a nucleic acid.

E) both a lipid and a nucleic acid.

Viruses are primarily classified according to their

A) type of nucleic acid.

B) type of life cycle.

C) number of chromosomes.

D) shape.

E) size.

Host specificity of a virus is due to

A) particular genes that it shares with the infected cell.

B) the presence of an envelope.

C) differences in size between the virus and the host cell.

D) the presence or absence of a cell wall on the host cell.

E) interactions between viral and cellular surface molecules.

Who was the first person to demonstrate the existence of viruses?

A) Stanley

B) Rous

C) Lacks

D) Ivanowsky

E) Prusiner

How are fungal viruses different from viruses that infect other organisms?

A) They have no extracellular state.

B) They have only DNA for genetic material.

C) They have no capsid.

D) They have no intracellular state.

E) They cannot pass through a filter.

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

Which of the following would NOT be found as a component of a bacteriophage?

A) envelope

B) icosahedral capsid

C) DNA

D) tail fibers

E) base plate

Which of the following statements regarding virus taxonomy is true?

A) Viruses are classified on the basis of the taxonomy of their host organisms.

B) Virus classes are well established.

C) Some virus family names are derived from the name of an important member of the family.

D) The species epithet is a Latin descriptor of the virion structure.

E) Virus classes are based on the domain of the host organism.

Which of the following statements comparing virus classification and taxonomy of

organisms is true?

A) Both viruses and organisms are organized into classes.

B) The common names of viruses are their genus and species epithet, as they are with organisms.

C) Both viruses and organisms are organized into domains.

D) Genus and specific epithet are used in both classification systems.

E) Only families are common to both viral classification and organism taxonomy.

Put the following stages of a lytic replication cycle in order, from earliest to latest stages:

I. Synthesis

II. Assembly

III. Attachment

IV. Release

V. Entry

A) III, V, I, II, IV

B) III, II, V, I, IV

C) V, III, II, IV, I

D) I, III, V, II, IV

E) I, II, III, V, IV

13) Which of the following is associated with the attachment of a bacteriophage to a bacterial

cell?

A) random collisions

B) chemical attractions

C) receptor specificity

D) chemical attractions and receptor specificity

E) random collisions, chemical attractions, and receptor specificity

14) The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection

cycle?

A) entry

B) assembly

C) entry and release

D) synthesis

E) attachment

The phenomenon of transduction is associated with which of the stages of a bacteriophage

infection cycle?

A) attachment

B) assembly

C) release

D) synthesis

E) entry

Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but

NOT in the lysogenic cycle?

A) attachment

B) entry

C) digestion of host DNA

D) viral protein synthesis

E) both digestion of host DNA and viral proteins synthesis

Why is lysogeny advantageous to a bacteriophage?

A) It speeds up the viral infection cycle.

B) The genetic material of the bacteriophage can be passed on to future generations of cells.

C) It allows the bacteriophage to infect cells it would not normally infect.

D) It allows the bacteriophage to destroy the host cell's DNA.

E) It enables the bacteriophage to take over the cell.

Which of the following agents is capable of inducing conversion of a prophage back to a

lytic phage?

A) UV light

B) X rays

C) presence of +ssRNA

D) UV light and X rays

E) UV light and +ssRNA

Zones of clearing in cell cultures that are the result of virus infection are called plaques.

Sometimes "cloudy plaques" are seen on bacterial cultures infected with bacteriophage. What

type of viral infection might cause this appearance?

A) lytic

B) lysogenic

C) prion

D) viroid

E) transducing

Which of the following is matched INCORRECTLY?

A) poliovirus — direct penetration

B) herpesvirus — endocytosis

C) adenovirus — membrane fusion

D) measles virus — membrane fusion

E) HIV — membrane fusion

Reverse transcriptase is associated with which of the following?

A) dsDNA viruses

B) +ssRNA viruses

C) -ssRNA viruses

D) retroviruses

E) dsRNA viruses

The genome of which of the following types of animal virus can act directly as mRNA?

A) retroviruses

B) +ssRNA viruses

C) -ssRNA viruses

D) ssDNA viruses

E) dsRNA viruses

Which of the following types of animal virus requires RNA-dependent RNA transcriptase to

be replicated?

A) +ssRNA viruses

B) ssDNA viruses

C) -ssRNA viruses

D) retroviruses

E) dsDNA viruses

In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of

the host cell. This fact implies that the viral genome may encode

A) reverse transcriptase.

B) a DNA polymerase.

C) RNA-dependent RNA transcriptase.

D) ribosome components.

E) reverse transcriptase and RNA-dependent RNA transcriptase.

Which of the following membranes can give rise to a viral envelope?

A) the nuclear membrane

B) the cytoplasmic membrane

C) the endoplasmic reticulum

D) the nuclear and cytoplasmic membranes

E) the nuclear and cytoplasmic membranes and the endoplasmic reticulum

The majority of cases of infant diarrhea are caused by what kind of virus?

A) dsDNA viruses

B) dsRNA viruses

C) +ssRNA viruses

D) retroviruses

E) -ssRNA viruses

How is the HIV provirus different from a lambda phage prophage?

A) The HIV provirus is integrated permanently into the host cell's DNA.

B) All subsequent generations of HIV-infected cells carry the provirus.

C) All the offspring of a cell infected with a prophage will contain the virus.

D) The HIV provirus is inactive inside the host cell.

E) Lambda phage-infected cells produce virus slowly over time.

Which of the following individuals discovered prions?

A) Lacks

B) Iwanowsky

C) Prusiner

D) Stanley

E) Rous

One mechanism by which viruses may cause cancer is to interrupt the genetic regulatory

sequences of repressor proteins. Which of the following types of viruses is most likely to be

involved in causing cancer by this mechanism?

A) +ssRNA viruses

B) dsRNA viruses

C) -ssRNA viruses

D) retroviruses

E) +ssRNA and -ssRNA viruses

Tumors invade other organs and tissues in a process called

A) neoplasia.

B) a plaque assay.

C) latency.

D) budding.

E) metastasis.

Plaque assays are used for

A) evaluating the cancer-causing ability of a virus.

B) estimating the number of phages in a culture.

C) the study of prions.

D) cultivating viruses that cannot be grown any other way.

E) counting the number of latent phages in a cell.

Diploid cell cultures and continuous cell cultures differ in which of the following ways?

A) longevity

B) source of cells

C) convenience of use

D) longevity and convenience of use

E) longevity and source of cells

Viroids infect

A) bacteria.

B) plants.

C) fungi.

D) plants and animals.

E) all organisms.

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.

The infectious particles of fungi have RNA genomes and lack a capsid. They are therefore

similar to

A) bacteriophages.

B) enveloped viruses.

C) prions.

D) viroids.

E) lysogens.

A lipid membrane is present

A) only in viruses.

B) in both cells and viruses.

C) only in cells.

D) only in prions.

E) in both prions and viroids.

Double-stranded DNA genomes are found

A) only in viroids.

B) only in cells.

C) only in viruses.

D) in both cells and viruses.

E) in both viruses and viroids.

Double-stranded RNA genomes can be found

A) only in cells.

B) in both cells and viruses.

C) only in viruses.

D) in prions.

E) in both prions and viruses.

Cytoplasm is a characteristic of

A) cells only.

B) viruses only.

C) both cells and viruses.

D) viroids only.

E) both viroids and viruses.

Proteins are present in

A) cells only.

B) viruses only.

C) viroids only.

D) both cells and viruses.

E) cells, viruses, and viroids.

Viruses are shed slowly and steadily during

A) lytic replication.

B) budding.

C) oncogenesis.

D) persistent infection.

E) latency.

During __________, viruses remain dormant in a cell.

A) budding

B) latency

C) lytic replication

D) persistent infection

E) oncogenesis

Virus replication results in the death of the cell in a(n) __________ infection.

A) lytic

B) latent

C) persistent

D) oncogenic

E) both latent and persistent

Virus infection results in cancer in the process of

A) lytic replication.

B) budding.

C) oncogenesis.

D) persistent infection.

E) latency.

is a mechanism of release for enveloped viruses.

A) Lytic replication

B) Persistent infection

C) Oncogenesis

D) Latency

E) Budding

Viruses cause most human cancers.

Most viruses cannot be seen by light microscopy.

Protozoa are susceptible to viral attack.

Many diseases of plants are caused by infectious RNA molecules lacking capsids.

Bacteriophages are cheaper and easier to culture than animal viruses.

Assembly of new viruses is a process that usually requires the direction of a variety of viral

and cellular enzymes.

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

Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for

the majority of dsDNA viruses.

Transcription of RNA from RNA does not occur in uninfected cells.

Virus vaccines are always cultured in embryonated chicken eggs.

The combination of a virus's protein coat and nucleic acid core is called the __________.

Viral capsids are composed of subunits called __________.

A(n) __________ is a 20-sided polyhedral capsid.

Bacteriophages use the enzyme __________ to breach the bacterial cell wall.

The number of new bacteriophages released from each infected cell is called the __________

size.

The process in which viral capsids are removed within the infected cell is called __________.

Virus RNA that can act directly as mRNA is __________-strand RNA.

RNA viruses such as HIV require the activity of reverse __________ to become proviruses.

In enveloped viruses, virus-encoded __________ proteins are required for the assembly of

the envelope around the capsid.

Genes that play a role in proper cell division but may also play a role in some types of cancer

are called __________.

A(n) __________ is a clear zone on a bacterial lawn where cells have been killed by the

activity of a bacteriophage.

Three __________ represent the highest level of taxonomic rank used in classifying viruses.

Prions are composed of a single protein called __________. (Be sure you use proper

capitalization.)

An animal virus that does not have an envelope is described as a(n) __________ virion.