Deck 25: The Viruses

Question 1

In which of the following stages of the viral infectious cycle do enveloped viruses usually acquire their envelopes?

A) penetration
B) component biosynthesis
C) assembly
D) release

Answer 1

D

Question 2

Which of the following represent(s) the way(s) in which enveloped viruses acquire their envelopes?

A) budding through the plasma membrane.
B) budding through internal cellular membranes.
C) Viral enzymes are responsible for production of the envelope.
D) For some viruses, a is correct; for other viruses, b is correct.

Answer 2

D

Question 3

The largest viruses known are the

A) herpesviruses.
B) hepadnaviruses.
C) adenoviruses.
D) mimiviruses.

Answer 3

D

Question 4

Which of the following uses dsRNA as the genome?

A) parvovirus
B) bunyavirus
C) reovirus
D) poxvirus

Question 5

For most T-even phages, the nucleic acid enters the host cell but the capsid is left outside.

Question 6

The tails of some bacteriophage

A) include a contractile sheath.
B) rotate like flagella to drive the phage genome into the cytoplasm of the host.
C) exhibit oar like motion that drives the phage genome into the cytoplasm of the host.
D) none of the choices

Question 7

A bacterium carrying a dormant phage inserted in the chromosome is called a __________.

Question 8

Late mRNA products in T4 phage include

A) phage structural proteins.
B) proteins that help with phage assembly without becoming part of the virion.
C) proteins involved in cell lysis and phage release.
D) all of the above

Question 9

Unlike most enveloped viruses, herpes viruses involve the host __________ membrane in the formation of their envelope.

A) plasma
B) nuclear
C) mitochondrial
D) none of these

Question 10

________ mRNA is synthesized before replication of the viral nucleic acid.

Question 11

A __________ infection is one in which the virus quits reproducing and remains dormant for a period before becoming active again.

A) persistent
B) latent
C) slow virus
D) none of these

Question 12

Virus morphology does not include which of the following characteristics?

A) size
B) shape
C) presence or absence of an envelope
D) host range

Question 13

Bacteriophage T4 blocks transcription of host genes using an enzyme that transfers an ______ from NAD onto the alpha subunit of RNA polymerase.

Question 14

The most common type of molecule found on the surface of animal viruses for interacting with host cell receptors is a(n)

A) lipoprotein.
B) glycoprotein.
C) phosphoprotein.
D) teichoic acid.

Question 15

Which of the following is(are) used in the classification of animal viruses?

A) virion morphology
B) genome structure
C) genetic relatedness
D) all of the choices

Question 16

For which of the following DNA viruses do(es) DNA replication occur in the cytoplasm rather than in the nucleus?

A) poxviruses
B) herpesviruses
C) adenoviruses
D) DNA replication occurs in the nucleus for all of these.

Question 17

Glucosylation of hydroxymethylcytosine residues protects phage T4 DNA from cleavage by bacterial restriction enzymes.

Question 18

Which of the following does not use RNA as the genome?

A) poxvirus
B) poliovirus
C) influenza virus
D) rabies virus

Question 19

__________ is an unusual base found in the DNA of T-even phages.

Question 20

Viruses infecting algae have never been detected.

Question 21

Phage T4 protects its DNA from cleavage by host restriction enzymes by

A) inactivating restriction enzymes.
B) substituting glucosylated hydroxymethylcytosine for cytosine.
C) methylating bases.
D) replicating very rapidly.

Question 22

Release of T4 phage from host cells after assembly

A) occurs by extrusion and does not result in cell lysis.
B) depends on a protein that interacts with MurA and interferes with normal peptidoglycan synthesis.
C) requires holin protein which allows the T4 lysozyme to attack the peptidoglycan.
D) occurs by exocytosis.

Question 23

Establishment of lysogeny by phage is usually influenced strongly by

A) the previous host infected by the virus.
B) components of the host replication machinery.
C) the physiological condition of the host at the time of infection.
D) none of the choices

Question 24

In viral infections involving double-stranded DNA viruses, all of the viral genes are usually expressed prior to the replication of viral nucleic acid.

Question 25

The latent form of a bacteriophage genome that exists when a phage establishes lysogeny is called a

A) lysogen.
B) prophage.
C) viroid.
D) prion.

Question 26

All bacteriophages infecting members of the Archaea possess genomes made of

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

Question 27

The protein required for the establishment and maintenance of lysogeny in cells infected with the temperate bacteriophage lambda is the

A) lac repressor.
B) lambda repressor.
C) lambda cos.
D) lambda Xis and Int proteins.

Question 28

Lysogeny always requires integration of the viral genome into the host chromosome.

Question 29

When a viral genome is integrated into the host chromosome but does not result in the lysis of the host cell, the condition is referred to as

A) temperate infection.
B) a virulent infection.
C) lysogeny.
D) a lytic infection.

Question 30

The sequence of genes in each T4 virus within a population is the same but starts with a different gene at the 5' end. If each of these linear pieces is circularized, the gene sequences would be identical. The T4 DNA, therefore, is described as being

A) two fold rotationally symmetrical.
B) a linear repeat.
C) circularly permuted.
D) linearly palindromic.

Question 31

Bacteriophage that only exhibit lytic replication cycles are called __________ phages.

A) temperate
B) virulent
C) intemperate
D) lytigate

Question 32

A _________________ is a sequence-specific recognition protein with endonuclease activity.

A) DNA Helicase
B) terminal transferase
C) restriction endonuclease
D) DNA ligase

Question 33

Entry of a virus into the lytic cycle after lysogeny has been established is called

A) lysogenic conversion.
B) lysogenic reversion.
C) induction.
D) none of the choices

Question 34

The cascade of events determining whether bacteriophage lambda elects to purpose lysogeny or a lytic cycle begins with a race between the production of the lambda repressor and

A) integrase.
B) N protein.
C) endolysin.
D) Cro protein.

Question 35

A bacteriophage that can integrate its genome into the host chromosome and not cause lysis of the host cell is said to be

A) virulent.
B) avirulent.
C) moderate.
D) temperate.

Question 36

_____________ are able to degrade infecting bacteriophage DNA, thus protecting the host cell.

A) Lysozyme
B) Protection exonucleases
C) Restriction endonucleases
D) Modification methylases

Question 37

Phage T4 gains release from the infected host cell like many other double stranded DNA phages by interfering with the activity of enzymes that synthesize peptidoglycan.

Question 38

In T-even phages, which of the following makes the initial contact with the appropriate receptor site?

A) tail fiber
B) base plate
C) collar
D) tail tube

Question 39

Once a virus establishes lysogeny, it may not switch to the lytic cycle at some later time.

Question 40

In the case of phage lambda, termination of lysogeny and entry into the lytic cycle usually occurs in response to environmental damage to the host DNA.

Question 41

Parvoviruses are among the simplest known DNA viruses of animals.

Question 42

Segmented genomes in negative-strand RNA viruses may have evolved from unsegmented ones; they may have been created by the reduction of redundant genetic regions.

Question 43

Because their host cells have dsDNA genomes, viruses with RNA genomes cannot rely on host cell enzymes for genome replication or mRNA synthesis.

Question 44

Retroviruses have a +ssRNA as their genome. In order to complete an infection, they must first make a __________ molecule, which they use to direct the synthesis of mRNA.

A) dsRNA
B) dsDNA
C) DNA:RNA hybrid
D) -ssRNA

Question 45

Tobacco mosaic virus can be transmitted between individual plants by biting insects.

Question 46

Which of the following uses ssDNA as the genome?

A) parvovirus
B) poliovirus
C) herpesvirus
D) poxvirus

Question 47

For bacteriophage with +ssRNA as their genome, which type of nucleic acid is used as the template for the production of more genomic RNA?

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

Question 48

The genomes of phiX174 and fd are

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

Question 49

A group of viruses that cause severe diarrhea, resulting in over 600,000 deaths worldwide annually is the

A) polioviruses.
B) rotaviruses.
C) poxviruses.
D) herpesviruses.

Question 50

Influenza virus adheres to the epithelium of the respiratory system with the aid of _________ and _________ found in its envelope spikes.

Question 51

Although poliovirus capsids contain several distinct proteins, these are synthesized as a single polypeptide then cleaved by proteases to produce the individual proteins.

Question 52

Attachment of a bacteriophage to its host requires

A) specific surface proteins on the bacteriophage.
B) specific receptor molecules on the host cell.
C) nucleic acid protein interactions.
D) specific surface proteins on the bacteriophage and specific receptor molecules on the host cell

Question 53

The enzyme used by retroviruses to make a DNA copy of their RNA genome is called

A) RNA polymerase.
B) DNA polymerase.
C) RNA replicase.
D) reverse transcriptase.

Question 54

One way in which small viruses package more information into a very small genome is to use overlapping genes so that the same base sequence is read in more than one reading frame.

Question 55

Which of the following must bring in a virion-associated RNA replicase when it infects host cells?

A) +ssRNA viruses
B) -ssRNA viruses
C) +dsRNA viruses
D) all of the choices

Question 56

When a _________ enters a host cell, it loses the outermost protein layer and is then referred to by virologists as a double-layered particle (DLP).

Question 57

Which of the following is not a function of the replicative form (dsDNA) of phage phiX174?

A) direct the synthesis of more RF copies
B) direct the synthesis of minus-stranded DNA
C) direct the synthesis of plus-stranded DNA
D) direct the synthesis of mRNA

Question 58

The genomes of _____________________ cannot function as mRNA and therefore these viruses must bring at least one RNA-dependent RNA polymerase into the host cell during entry.

A) positive-strand RNA viruses
B) double-stranded DNA viruses
C) negative-strand RNA viruses
D) single-stranded DNA viruses

Question 59

In order for bacteriophage to be released from the host by a lysis mechanism, enzymes are required that

A) halt ATP synthesis.
B) stabilize the cytoplasmic membrane and cell wall.
C) damage the cell wall and cytoplasmic membrane.
D) degrade the host chromosome.

Question 60

Almost all known plant viruses are RNA viruses.

Question 61

After infecting the cell, HBV's gapped DNA is released into the nucleus where host _______ enzymes fill the gap and seal the nick, yielding a covalently closed, circular DNA.

Question 62

The HBV genome is a circular dsDNA molecule that consists of

A) one complete but nicked strand.
B) segmented DNA.
C) a complementary strand.
D) one complete but nicked strand and a complementary strand.

Question 63

Hepatitis B virus is an example of a DNA virus that uses reverse transcriptase in its replication cycle.