Chapter 25 Microbiology

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8. 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.

True

False

9. 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.

True

False

10. 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.

True

False

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

True

False

12. Parvoviruses are among the simplest known DNA viruses of animals.

True

False

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

True

False

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

True

False

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

Virion morphology

Genome structure

Genetic relatedness

All of the choices

16. Viruses infecting algae have never been detected.

True

False

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

Persistent

Latent

Slow virus

None of these

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

True

False

19. Almost all known plant viruses are RNA viruses.

True

False

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

True

False

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

Lipoprotein

Glycoprotein

Phosphoprotein

Teichoic acid

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

True

False

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

Temperate

Virulent

Intemperate

Lytigate

24. Virus morphology does not include which of the following characteristics?

Size

Shape

Presence or absence of an envelope

Host range

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

Tail fiber

Base plate

Collar

Tail tube

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

True

False

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

Lac repressor.

Lambda repressor.

lambda cos.

Lambda Xis and Int proteins.

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

Polioviruses

Rotaviruses

Poxviruses

Herpesviruses

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

Lysogenic conversion. 

lysogenic reversion.

Induction

None of the choices

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

Inactivating restriction enzymes.

substituting glucosylated hydroxymethylcytosine for cytosine. 

Methylating bases. 

Replicating very rapidly.

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

DNA Helicase

Terminal transferase

Restriction endonuclease  

DNA ligase

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

Virulent

Avirulent

Moderate

Temperate

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

Plasma

Nuclear

Mitochondrial

None of these

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

Lysogen

Prophage

Viroid

Prion

35. Establishment of lysogeny by phage is usually influenced strongly by

The previous host infected by the virus. 

Components of the host replication machinery.

The physiological condition of the host at the time of infection. 

None of the choices

36. Attachment of a bacteriophage to its host requires

specific surface proteins on the bacteriophage.  

Specific receptor molecules on the host cell.

Nucleic acid protein interactions.  

Specific surface proteins on the bacteriophage and specific receptor molecules on the host cell

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

halt ATP synthesis.

Stabilize the cytoplasmic membrane and cell wall.  

Damage the cell wall and cytoplasmic membrane.

Degrade the host chromosome.

38. Which of the following uses ssDNA as the genome?

Parvovirus

Poliovirus

Herpesvirus

Poxvirus

39. The tails of some bacteriophage

Include a contractile sheath.

Rotate like flagella to drive the phage genome into the cytoplasm of the host.

Exhibit oar like motion that drives the phage genome into the cytoplasm of the host.

None of the choices

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

Budding through the plasma membrane. 

budding through internal cellular membranes. 

Viral enzymes are responsible for production of the envelope. 

For some viruses, a is correct; for other viruses, b is correct.

41. The largest viruses known are the

Herpes viruses

Hepadnaviruses

Adenoviruses

Mimiviruses

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

Lysozyme

Protection exonucleases 

Restriction endonucleases

Modification methylases

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

Poxvirus

Poliovirus

Influenza virus

Rabies virus

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

Penetration

Component biosynthesis

Assembly

Release

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

Direct the synthesis of more RF copies 

Direct the synthesis of minus-stranded DNA

Direct the synthesis of plus-stranded DNA 

Direct the synthesis of mRNA

46. All bacteriophages infecting members of the Archaea possess genomes made of

DsDNA

SsDNA

DsRNA

SsRNA

47. 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

Integrase

N protein.

Endolysin

Cro protein.

48. Release of T4 phage from host cells after assembly

Occurs by extrusion and does not result in cell lysis.

Depends on a protein that interacts with MurA and interferes with normal peptidoglycan synthesis.

Requires holin protein which allows the T4 lysozyme to attack the peptidoglycan.

Occurs by exocytosis.

49. 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

Two fold rotationally symmetrical.

A linear repeat. 

Circularly permuted.

Linearly palindromic.

50. 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

temperate infection. 

A virulent infection.

Lysogeny

a lytic infection.

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

+ssRNA viruse

-ssRNA viruses

+dsRNA viruses

all of the choices

52. 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.

Positive-strand RNA viruses  

Double-stranded DNA viruses  

Negative-strand RNA viruses

single-stranded DNA viruses

53. The HBV genome is a circular dsDNA molecule that consists of

One complete but nicked strand.

Segmented DNA.

A complementary strand.  

One complete but nicked strand and a complementary strand.

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

True

False

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

True

False

56. 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.

DsRNA

DsDNA

DNA:RNA hybrid

-ssRNA

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

RNA polymerase.

DNA polymerase.

RNA replicase.

Reverse transcriptase.

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

-ssRNA

DsRNA

SsDNA

DsDNA

59. Which of the following uses dsRNA as the genome?

Parvovirus

Bunyavirus

Reovirus

Poxvirus

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

Poxviruses

Herpes viruses

Adenoviruses

DNA replication occurs in the nucleus for all of these.

61. The genomes of phiX174 and fd are

Double stranded DNA.

Single stranded DNA.

Double stranded RNA.

Single stranded RNA.

62. Late mRNA products in T4 phage include

Phage structural proteins.

Proteins that help with phage assembly without becoming part of the virion.

Proteins involved in cell lysis and phage release.

All of the above

63. 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.

True

False