Deck 9: Viruses and Virology

Question 1

What genome composition makes viruses most susceptible to destruction by prokaryotic restriction endonucleases?

A) dsRNA
B) ssDNA
C) ssRNA
D) dsDNA

Answer 1

D

Question 2

An integrated stable genetic element in a eukaryotic cell

A) is called a provirus.
B) can occur anywhere in the cellular DNA.
C) is analogous to the integration of phage DNA into a bacterial genome.
D) is all of the above.

Answer 2

D

Question 3

Which statement is TRUE?

A) Many viruses contain their own nucleic acid polymerases.
B) All viruses contain their own nucleic acid polymerases.
C) Viruses do not contain their own nucleic acid polymerases.
D) The origins of the nucleic acid polymerases used by viruses are eukaryotic.

Answer 3

A

Question 4

When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus

A) concatemer.
B) nucleocapsid.
C) envelope.
D) capsid.

Question 5

All viral particles

A) exhibit cell lysis under a particular condition.
B) are metabolically inert.
C) contain an envelope to prevent its degradation outside of a host.
D) are smaller than bacterial cells.

Question 6

Viral size is generally measured in

A) micrometers.
B) picometers.
C) centimeters.
D) nanometers.

Question 7

Viral replication is

A) dependent on the cell's chromosomes but independent of the cell itself.
B) independent of the cell's chromosomes but dependent on the cell itself.
C) independent of both the cell's chromosomes and the cell itself (although the cell does provide a convenient matrix for replication).
D) dependent on both the cell's chromosomes and the cell itself.

Question 8

A viroid

A) is a small, circular ssRNA molecule.
B) lacks protein- encoding genes.
C) lacks a capsid.
D) is characterized by all of the above.

Question 9

Cellular receptors may be composed of

A) proteins.
B) lipids.
C) carbohydrates.
D) combinations of any or all of the above.

Question 10

The simplest form of viral reproduction in RNA viruses is that which occurs with the

A) negative- strand RNA viruses.
B) positive- strand DNA viruses.
C) positive- strand RNA viruses.
D) negative- strand DNA viruses.

Question 11

The packaging mechanism of T4 DNA involves cutting of DNA from

A) linear genetic elements.
B) DNA concatemers.
C) circular genetic elements.
D) none of these; they are all transcribed directly from inserted viral DNA.

Question 12

A prophage replicates

A) independently of its host while the lytic genes are expressed.
B) independently of its host while the lytic genes are not expressed.
C) along with its host while the lytic genes are expressed.
D) along with its host while the lytic genes are not expressed.

Question 13

Retroviruses

A) include the virus that causes AIDS.
B) transcribe DNA from RNA template.
C) may cause cancer.
D) do all of the above.

Question 14

Reverse transcriptase is a(n)

A) RNA- dependent RNA polymerase.
B) DNA- dependent RNA polymerase.
C) RNA- dependent DNA polymerase.
D) DNA- dependent DNA polymerase.

Question 15

Bacteriophages' genomes are typically composed of

A) double- stranded RNA.
B) single- stranded DNA.
C) double- stranded DNA.
D) single- stranded RNA.

Question 16

Enveloped viral membranes are generally with associated virus- specific .

A) lipid bilayers / glycoproteins
B) lipid bilayers / phospholipids
C) protein bilayers / lipids
D) glycolipid bilayers / phospholipids

Question 17

Which T bacteriophage has been studied most extensively?

A) T7
B) T6
C) T4
D) T2

Question 18

A virus that kills its host is said to be

A) virulent or lysogenic, but not temperate.
B) lysogenic.
C) temperate.
D) lytic or virulent.

Question 19

Lambda is

A) a linear double- stranded DNA phage.
B) a temperate phage that infects Escherichia coli.
C) replicated by the rolling circle mechanism.
D) all of the above.

Question 20

Plant viruses can be difficult to work with because

A) plant viruses often require a break in the plant cell wall to initiate infection.
B) their study sometimes requires the use of the whole plant.
C) plants typically grow much slower than bacteria.
D) All of the above are factors.

Question 21

Regarding the viral membrane in an enveloped virus, the lipids are derived from the
, and the proteins are encoded by _ .

Question 22

Bacteriophage Lambda integrates into an E. coli genome by the action of .

Question 23

Two chemical modifications of viral DNA that work to avoid host restriction mechanisms are and .

Question 24

Which of the following are the hosts for most enveloped viruses?

A) Archaea
B) animals
C) Bacteria
D) fungi

Question 25

Viruses infecting are typically the easiest to grow in the laboratory.

A) plants
B) prokaryotes
C) fungi
D) animals

Question 26

The process of copying information found in RNA into DNA is called .

Question 27

The Nobel Prize laureate David Baltimore is credited with the discovery of

A) retroviruses and reverse transcriptase.
B) T- series viruses (such as T2, T4, etc.).
C) parvoviruses.
D) prions.

Question 28

Lambda and other temperate viruses have an exceedingly complex genetic switch that
.

Question 29

Restriction is

A) a general host mechanism to prevent the invasion of foreign nucleic acid.
B) the viral process whereby the virus prevents other viruses from entering the cell.
C) a general host mechanism to prevent virus particles from further infective action.
D) the viral process whereby a host's DNA ceases normal functioning.

Question 30

Avirulent prions consist largely of , whereas pathogenic prions have more
regions.

Question 31

T4 bacteriophage contains 5- hydroxymethylcytosine that replaces and is a protectant against _.

Question 32

The virus repressor protein

A) has different actions in different situations.
B) does not control the prophage's lytic genes but does control the incoming genomes of the same virus.
C) controls the prophage's lytic genes but not the incoming genomes of the same virus.
D) controls both the lytic genes on the prophage and prevents an incoming virus of the same type.

Question 33

Present in both animals and plants, are incomplete and therefore require the presence of other active helper viruses.

Question 34

The smallest unit that causes a detectable effect when added to a susceptible host is known as a(n) .

Question 35

The term "phage" is generally reserved for the viruses that infect .

Question 36

The primer for retrovirus reverse transcription is a specific

A) nuclear tRNA.
B) nuclear tDNA.
C) tRNA encoded by the cell.
D) tRNA encoded by the virus.

Question 37

Viral replication occurs

A) extracellularly.
B) intracellularly.
C) both intracellularly and extracellularly.
D) either intracellularly or extracellularly, depending on the virus involved.

Question 38

Rod- shaped viruses have symmetry, and spherical viruses have _ symmetry.

Question 39

Animal viruses are more easily lysed compared to prokaryotic cells, because animal host cells .

Question 40

Viral proteins are categorized as early and late. Early proteins are , while late proteins include .

Question 41

DNA viruses, along with cells in Archaea, Bacteria, and Eukarya, all follow the central dogma of molecular biology.

Question 42

An RNA genome itself serves as mRNA in negative- stranded RNA viruses.

Question 43

The use of has greatly enhanced research on most animal and many plant viruses.

Question 44

Temperate viruses can enter into either a lytic or lysogenic cycle.

Question 45

RNA viruses encode host restriction systems designed to destroy host DNA.

Question 46

Tailed bacterial viruses can be used as genetic engineering tools.

Question 47

A temperate virus does not exist as a virus particle inside the host cell.

Question 48

In viruses, genetic information flows from to .

Question 49

Transmissible spongiform encephalopathies (TSEs) are caused by .

Question 50

A cell that allows the complete replication cycle of a virus to take place is said to be a(n)
.

Question 51

Virions infecting some bacteria possess the enzyme _ that makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.

Question 52

The virus repressor protein provides immunity to infection by the same type of virus.

Question 53

Viruses can confer additional properties on their host cells, which can in turn be inherited.

Question 54

The Baltimore Classification System groups seven viral classes according to and
.

Question 55

A cell infected with T4 phage undergoes cell lysis because the virus codes for , which acts by _ .

Question 56

The number of infectious plaque forming units (pfu) per volume of fluid is known as the
.

Question 57

The two events necessary to establish lysogeny for lambda phage are and
.

Question 58

When a virus enters a host cell in which it can replicate, the process is called a(n) .

Question 59

A clearing of no host cells among a lawn of growing host cells is known as a(n) , which in principle represents .

Question 60

Whether lambda phage undergoes the lytic or lysogenic cycle is dependent on the presence or absence of .

Question 61

Viruses can redirect host metabolic functions.

Question 62

Penetration requires that the entire virus is inserted within the host.

Question 63

Some viruses possess icosahedral heads and helical tails.

Question 64

Because a prion is composed entirely of protein, explain how the prion replicates.

Question 65

Why is uncoating a step in the replication cycle of some animal viruses?

Question 66

Describe the structure of the T4 virus, and explain this virus's attachment and penetration processes in terms of this structure.

Question 67

Lysogeny is unique to bacteriophages; similar relationships have not been found among the animal viruses.

Question 68

Although T4 encodes over 250 proteins, it does not encode its own RNA polymerase.

Question 69

There is at least one known virus whose genome is actually larger than a cellular genome.

Question 70

Describe the process whereby dsDNA viruses are replicated.

Question 71

Patrick Forterre's hypothesis states that an RNA virus infected a cell to form the last universal common ancestor (LUCA).

Question 72

How does efficiency of plating affect plaque- forming units?

Question 73

A lytic infection results in death of the host cell.

Question 74

Currently there is no formal system of viral taxonomy, although several systems are presently being developed.

Question 75

In the first few minutes after host cell infection, the virus undergoes an eclipse.

Question 76

Describe the seven steps of retroviral replication.

Question 77

In the context of biogeochemical cycling, explain the role of bacteriophages and their impact on carbon cycling in the oceans.

Question 78

Viruses have both an intracellular and an extracellular form.

Question 79

Explain the difference between an enveloped virus and a naked virus.

Question 80

Explain the concept of a persistent infection in terms of a virus- infected cell.