Micro Ch. 6

82) What is the minimum number of phage that can initiate the development of a plaque in a bacterial lawn? A) 1 B) 5 C) 10 D) 25

A) 1

87) Diseases caused by prions that are seen in domesticated animals and humans have which of the following manifestations in common? A) All diseases cause neurodegeneration B) All diseases cause gastrointestinal upset C) All diseases affect the cardiovascular system D) All diseases affect the musculoskeletal system E) All diseases cause skin lesions

A) All diseases cause neurodegeneration

31) Which of the following is true of a viral DNA genome? A) It uses the same four nitrogenous bases found in prokaryotic and eukaryotic DNA. B) It may have the normal bases found in prokaryotic and eukaryotic DNA, or it may have one or more unusual bases. C) It is usually composed of unusual bases unique to viruses. D) Viruses use only RNA for their genome

A) It uses the same four nitrogenous bases found in prokaryotic and eukaryotic DNA.

77) Which of the following encodes its own capsid proteins? A) Satellite virus B) Satellite DNA C) Satellite RNA D) Prion

A) Satellite virus

61) Prions are of significance because they cause infections of ________. A) domestic animals and humans B) plants C) fungi D) prokaryotes

A) domestic animals and humans

71) The production of cholera toxin by virulent strains of Vibrio cholera is dependent upon genes in a bacteriophage. This is an example of ________. A) lysogenic conversion B) induction C) bacterial transformation D) transduction

A) lysogenic conversion

59) Viroids are of economic significance because they cause disease in ________. A) plants B) animals C) humans D) All of the choices are correct

A) plants

35) Most enveloped viruses use the host ________ membrane as their envelope source. A) plasma B) nuclear C) mitochondrial D) None of these choices are correct

A) plasma

32) Virion size ranges from ________. A) 1-40 nm B) 10-400 nm C) 600-1,000 nm D) 1,000-10,000 nm

B) 10-400 nm

51) 0.2 mls of a 10-4 dilution of a virus preparation yields 90 plaques. What is the number of PFU per ml in the undiluted virus preparation? A) 9.0 × 105 B) 4.5 × 106 C) 4.5 × 107 D) 9.0 × 108

B) 4.5 × 106

46) Which of the following has been associated with a form of liver cancer? A) Human papilloma virus B) Hepatitis B virus C) Human T-cell lymphotropic virus D) Hepatitis A virus

B) Hepatitis B virus

70) For a temperate phage to produce more phage, which of the following must happen? A) Lysogeny B) Induction C) Lysogenic conversion D) Prophage formation

B) Induction

68) Which type of virus is most likely to be released by lysis of the host cell? A) Enveloped virus B) Nonenveloped virus

B) Nonenveloped virus

3) Which is not true of viruses? A) They can exist in an intracellular or extracellular phase. B) They infect animal and plant cells only. C) They can be observed with an electron microscope. D) They are acellular. E) They replicate only inside host cells.

B) They infect animal and plant cells only

73) Which type of phage always lyses its host cell? A) Temperate B) Virulent C) Lysogenic D) Prophage

B) Virulent

79) The most notable difference between PrPC (normal protein) and PrPSc (prion protein) is ________. A) PrPC is a much longer polypeptide chain, compared to PrPSc B) PrPC causes a cell to undergo rapid apoptosis C) PrPc folds appropriately whereas PrPSc does not fold correctly D) PrPc is a functional glycolytic enzyme whereas PrPSc is nonfunctional

C) PrPc folds appropriately whereas PrPSc does not fold correctly

67) Which virion release process is most often used by enveloped viruses? A) Lysis B) Facilitated diffusion C) Budding D) Diffusion through channel protein

C) Budding

19) The simplest viruses consist of ________. A) RNA only B) protein only C) RNA or DNA in a protein coat D) RNA or DNA in a protein coat covered with lipid envelope E) RNA, DNA, and enzymes in a protein coat with a lipid envelope

C) RNA or DNA in a protein coat

76) Place the steps in the correct order to reflect how a lethal dose may be determined. 1. Dilutions of virus are made to represent a range of concentrations. 2. Dilutions are inoculated into susceptible tissue cultures (or susceptible host organisms). 3. Inoculated host cells are observed and the number of dead cells are counted. 4. The dilution which killed 50% of the tissue culture cells is identified.

1, 3, 2, 4

85) Place the steps of viral replication in the correct order. 1. Attachment to host cell 2. Entry into host cell 3. Synthesis of nucleic acids and proteins 4. Self-assembly of nucleocapsids 5. Release from host cell

2, 4, 5, 1, 3

74) Place the following steps in the correct order to reflect how a plaque assay is done. 1. Several dilutions of sample to be assayed are prepared. 2. Dilutions are mixed with the appropriate bacterial host. 3. Bacterial/sample dilution mixtures are plated on agar plates. 4. Plates are incubated to allow for plaque development. 5. Plates from different dilutions are examined and plaques are counted

4,1, 5, 2, 3

53) Hemagglutination is ________. A) the clumping together of red blood cells in the presence of a viral suspension B) the binding of iron in the process of a viral suspension C) the clumping together of infected cells in the presence of a viral suspension D) None of the choices are correct.

A) the clumping together of red blood cells in the presence of a viral suspension

86) Virulent and temperate phages differ in that ________. A) virulent phages always result in the lysis of the host cell, whereas temperate phages may lyse the host cell, or they can enter a lysogenic cycle whereby they integrate their genome into the genome of the host cell B) temperate phages always result in the lysis of the host cell, whereas virulent phages may lyse the host cell, or they can enter a lysogenic cycle whereby they integrate their genome into the genome of the host cell C) temperate phages integrate their genome into that of the host cell, causing uncontrolled growth and ultimately lysis of the cell, whereas virulent phages remain in the lysogenic phase indefinitely D) virulent phages cause mutations in the host cell genome, whereas temperate phages have no genetic effect on the host cell

A) virulent phages always result in the lysis of the host cell, whereas temperate phages may lyse the host cell, or they can enter a lysogenic cycle whereby they integrate their genome into the genome of the host cell

22) Some complex viruses have icosahedral symmetry in the head region and helical symmetry in the tail. Overall, these viruses are said to have ________ symmetry. A) bilateral B) binal C) complex D) radial

B) binal

30) The protein coat surrounding the viral genome is called the ________. A) capsule B) capsid C) matrix D) envelope

B) capsid

43) Human cancer-causing viruses most often have a ________ genome. A) ssDNA B) dsDNA C) ssRNA D) dsRNA

B) dsDNA

37) Nonenveloped viruses most often gain access to eukaryotic host cells by ________. A) fusion with the host cell plasma membrane followed by entrance of the nucleocapsid into the cytoplasm B) endocytosis C) pinocytosis D) nucleic acid injection through the plasma membrane

B) endocytosis

23) Glycoprotein spikes protruding from the outer surface of viral envelopes function as ________. A) toxins B) factors that bind to host cells C) cell lysis factors D) factors needed for site specific recombination

B) factors that bind to host cells

28) Two major types of symmetry found in viruses include ________. A) icosahedral and radial B) icosahedral and helical C) helical and radial D) radial and bilateral

B) icosahedral and helical

21) In an enveloped virus, the part of the virus including the nucleic acid genome and the surrounding protein coat but not the envelope is called the ________. A) capsid B) nucleocapsid C) matrix D) virion

B) nucleocapsid

44) Adult T-cell leukemia is thought to be caused by ________. A) herpesviruses B) retroviruses C) parvoviruses D) picornaviruses

B) retroviruses

24) A ________ genome exists as several separate, nonidentical molecules that may be packaged together or separately. A) diploid B) segmented C) polyploid D) fractionated

B) segmented

33) Viral capsids are generally constructed without any outside aid once the subunits have been synthesized. This process is called ________. A) facilitated assembly B) self-assembly C) spontaneous maturation D) self-maturation

B) self-assembly

26) Which of the following is/are not true about viral envelopes? A) The envelope proteins are virus specific. B) The envelope lipids and carbohydrates are derived from the host. C) They are typical lipid monolayers with embedded viral proteins. D) The envelope proteins are virus specific and the envelope lipids and carbohydrates are derived from the host.

C) They are typical lipid monolayers with embedded viral proteins.

4) Which of the following is true of viruses in the extracellular phase? A) They possess many different enzymes. B) They can reproduce independently of living cells but only at a slow rate. C) They behave as a macromolecular complex and are no more alive than are ribosomes. D) They possess many different enzymes and they can reproduce independently of living cells but only at a slow rate.

C) They behave as a macromolecular complex and are no more alive than are ribosomes.

57) Which of the following is not a mechanism by which viruses cause cancer? A) They carry a cancer-causing gene into the cell. B) They encode proteins that bind to and inactivate host cell proteins known as tumor suppressor proteins. C) They produce defective interfering particles. D) An expression of viral proteins results in abnormal expression of genes that regulate cell growth and reproduction

C) They produce defective interfering particles.

6) The nucleic acids carried by viruses usually consist of ________. A) DNA B) RNA C) either DNA or RNA D) both DNA and RNA simultaneously

C) either DNA or RNA

36) Poliovirus receptors are found ________. A) in cells of all tissues B) in spinal cord anterior horn cells only C) in nasopharynx, gut, and spinal cord anterior horn cells D) in gut cells only

C) in nasopharynx, gut, and spinal cord anterior horn cells

25) Many of the enzymes found in virus particles are ________. A) required for viral attachment to host cells B) involved in viral entry into host cells C) involved in the replication of viral nucleic acid D) All of the choices are correct.

C) involved in the replication of viral nucleic acid

45) Genes whose expression (or abnormal expression) cause cancer are called ________. A) cancer genes B) progenes C) oncogenes D) carcinogens

C) oncogenes

52) A ________ assay is most useful for determining the viability of a viral preparation. A) direct (electron microscopic) count B) hemagglutination C) plaque D) PCR

C) plaque

20) Viral capsid protein subunits are called ________. A) auxomers B) elastomers C) protomers D) viromers

C) protomers

5) A complete virus particle is called a ________. A) capsid B) nucleocapsid C) virion D) cell

C) virion

27) Viral envelopes are composed of ________. A) proteins B) lipids C) carbohydrates D) All of the choices are correct

D) All of the choices are correct

49) Animal viruses have been cultivated in ________. A) suitable host animals B) embryonated eggs C) tissue cultures (monolayers of animal cells) D) All of the choices are correct

D) All of the choices are correct

50) Which of the following can be used to cultivate plant viruses? A) Cultures of separated plant cells B) Whole plants C) Plant protoplast cultures D) All of the choices are correct

D) All of the choices are correct

62) Which of the following diseases is (are) caused by prions? A) Scrapie B) Mad cow disease C) Kuru and Creutzfeldt-Jakob Disease D) All of the choices are correct.

D) All of the choices are correct.

58) Which of the following is not true of viroids? A) Viroids are small circular ssRNA molecules. B) Viroids have no protein capsids. C) Viroid RNA does not serve as mRNA nor does it direct the synthesis of mRNA. D) Extracellular viroids have a lipid bilayer envelope

D) Extracellular viroids have a lipid bilayer envelope

78) Which of the following is/are necessary for the replication of a satellite virus? A) Host cell only B) Helper virus only C) Prion only D) Host cell and helper virus

D) Host cell and helper virus

11) Virus morphology does not include which of the following characteristics? A) Size B) Shape C) Presence or absence of an envelope D) Host range

D) Host range

34) 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

D) Release

38) 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) Some viruses bud through the plasma membrane while other bud through internal cellular membranes.

D) Some viruses bud through the plasma membrane while other bud through internal cellular membranes.

7) Which of the following is not true of viruses? A) Viruses are acellular. B) Viruses consist of one or more molecules of DNA or RNA enclosed in a coat of protein and sometimes in other more complex layers. C) Viruses can exist in two phases: intracellular and extracellular. D) Viruses replicate by binary fission.

D) Viruses replicate by binary fission.

72) Diphtheria toxin is produced only by strains of Corynebacterium diphtheriae that are infected with a particular bacteriophage. This is an example of ________. A) conjugation B) induction C) lysis D) lysogenic conversion

D) lysogenic conversion

29) The function of the viral protein coat is to ________. A) protect the viral genetic material B) aid in the transfer of the viral genetic material between host cells C) elicit the production of protective antibodies D) protect the viral genetic material and aid in the transfer of the viral genetic material between host cells

D) protect the viral genetic material and aid in the transfer of the viral genetic material between host cells

60) Viroids are ________. A) proteins that may infect man and other animals causing spongiform encephalopathy B) a class of so-called slow viruses C) a new class of small single stranded DNA viruses that infect some animals D) short infectious single stranded RNAs that can infect some plants

D) short infectious single stranded RNAs that can infect some plants

80) All of the following are methods of prion disease transmission EXCEPT ________. A) ingestion of infected tissue B) inheritance (genetic) C) organ or tissue transplantation D) contamination through use of inadequately processed surgical instruments E) inhalation (airborne)

E) inhalation (airborne)

1) Viruses have typical cellular structure like other living organisms.

False

17) The presence or absence of an envelope is not useful in classifying viruses because any given virus may at one time have an envelope and at another time not have an envelope.

False

48) In a plaque assay, the number of infectious virions is usually identical to the number of virus particles present

False

54) Like bacteria and eukaryotic microorganisms, most viruses can be cultured using artificial media.

False

55) Bacterial viruses are so named because they have prokaryotic cell structures similar to their bacterial hosts.

False

66) There are no known human diseases that have been linked to prions

False

69) A temperate phage always lyses its host cell.

False

75) Laboratory animals must be used to determine lethal and infectious doses of viruses

False

8) Viruses infecting protists, including algae, have never been detected

False

81) A PrPc protein can convert a PrPSc to a PrPc.

False

10) Almost all known plant viruses are RNA viruses.

True

15) The most common capsid morphologies are icosahedral and helical.

True

16) The largest of the viruses are similar in size to some small bacteria and are large enough to be seen with a light microscope.

True

18) Viruses such as MS2 and Qß pack additional information into their genomes through the use of overlapping genes

True

2) Viruses in the extracellular state possess few, if any, active enzymes

True

39) Virus receptors are often not distributed uniformly over the surface of host cells, but are instead concentrated in lipid rafts.

True

40) Enveloped viruses may enter their host cells by fusion of their envelope with the cytoplasmic membrane, thereby depositing their nucleocapsid within the cell

True

41) Enveloped viruses may enter their host cells by engulfment within coated vesicles (endocytosis).

True

63) Prions consist of proteins and have no apparent nucleic acid genome.

True

64) Available evidence is consistent with the proposal that prion diseases are caused by infectious proteins.

True

65) The mechanism of pathogenesis by prions may involve a conformational change in the prion protein (PrP) to an abnormal form.

True

83) Creutzfeldt-Jacob disease is known to have been transmitted by surgical instruments and transplanted nerve tissue.

True

9) 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

84) Viruses can infect all known cell types. Specifically, the viruses that infect bacterial cells are called ________.

bacteriophages

13) Icosahedral viruses are constructed from ring- or knob-shaped units called ________.

capsomers

47) Microscopic or macroscopic degenerative changes or abnormalities in infected host cells and tissues are called ________ ________.

cytopathic effects

14) Viruses that are polyhedrons with 20 sides are said to have ________ symmetry.

icosahedral

56) Localized areas of destruction occurring on plants that have been infected by a virus are referred to as ________ lesions

necrotic

12) ________ are glycoprotein spikes that protrude from the outer surface of the viral envelope.

peplomers

42) Some viruses cause abnormal growth of cells rather than destruction. This is called ________.

transformation