Chapter 18-19

Last update by mayurcooled on 04/23/2014
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What is the function of reverse transcriptase in retroviruses?



A. It converts host cell RNA into viral DNA. B. It hydrolyzes the host cell's DNA. C. It uses viral RNA as a template for DNA synthesis.
D. It translates viral RNA into proteins. E. It uses viral RNA as a template for making complementary RNA strands.

Answer:
C. It uses viral RNA as a template for DNA synthesis.

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Related Quiz Content
  • smiraclelynch
    Answered in Chapter 18-19
    Refer to the treatments listed below to answer the following questions.

    You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.
    I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious
    II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope
    III. culturing the substance by itself on nutritive medium, away from any plant cells
    IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious


    Which treatment could definitively determine whether or not the component is a viroid?
    Student Response Correct Answer A. I
    B. II C. III D. IV E. first II and then III
    A. I
  • smiraclelynch
    Answered in Chapter 18-19
    Refer to the treatments listed below to answer the following questions.

    You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.
    I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious
    II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope
    III. culturing the substance by itself on nutritive medium, away from any plant cells
    IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious


    Which treatment would you use to determine if the agent is a prion?



    A. I only B. II only C. III only D. IV only
    E. either I or IV
    D. IV only
  • smiraclelynch
    Answered in Chapter 18-19
    The difference between vertical and horizontal transmission of plant viruses is that


    A. vertical transmission is the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species. B. vertical transmission is the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size. C. vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type. D. vertical transmission is the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level. E. vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.
    E. vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.
  • smiraclelynch
    Answered in Chapter 18-19
    What are prions?



    A. viral DNA that has had to attach itself to the host genome B. viruses that invade bacteria C. a mobile segment of DNA D. misfolded versions of normal brain protein
    E. tiny molecules of RNA that infect plants
    D. misfolded versions of normal brain protein
  • smiraclelynch
    Answered in Chapter 18-19
    Viruses can vary with respect to all of the following characteristics except _____. (Overview)


    the type of host cell it can infect

    the presence or absence of metabolic machinery

    DNA or RNA as the genetic material

    single- or double-stranded nucleic acids

    the presence or absence of a membranous envelope
    the presence or absence of metabolic machinery
  • smiraclelynch
    Answered in Chapter 18-19
    A microbiologist analyzes chemicals obtained from an enveloped RNA virus that infects monkeys. He finds that the viral envelope contains a protein characteristic of monkey cells. Which of the following is the most likely explanation? ( Concept 19.1)


    The viral envelope forms as the virus leaves the host cell.

    Its presence is a result of the monkey's immunological response.

    The virus fools its host by mimicking its proteins.

    The virus forced the monkey cell to make proteins for its envelope.

    The virus is a prophage.
    The viral envelope forms as the virus leaves the host cell.
  • smiraclelynch
    Answered in Chapter 18-19
    Which of the following, if any, may be a component of a virus? (Concept 19.1)


    protein

    double-stranded (ds) DNA

    phospholipid bilayer

    single-stranded (ss) RNA

    All of the listed responses are correct.
    All of the listed responses are correct.
  • smiraclelynch
    Answered in Chapter 18-19
    Viruses that infect bacteria are called _____. ( Concept 19.1)


    retroviruses

    bacteriophages

    proviruses

    capsomeres

    bacterioviruses
    bacteriophages
  • smiraclelynch
    Answered in Chapter 18-19
    HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because _____. ( Concept 19.2)


    the virus binds to specific receptors that are only present on certain immune cells

    other cells produce toxins that destroy the virus before infection can take place

    infection requires the presence of a specific DNA sequence that is only present in the genome of certain immune system cells

    the virus gets into all cells, but the viral RNA is immediately destroyed in all but a small number of immune system cells

    the virus is not very mobile within the body and only comes into contact with a limited number of immune cells
    the virus binds to specific receptors that are only present on certain immune cells
  • smiraclelynch
    Answered in Chapter 18-19
    Cancer cells often have protein receptor molecules on their surfaces that differ from those on normal body cells. Given this fact, how might viruses be used to treat cancer? ( Concept 19.2)


    Viruses could be engineered to infect only cancer cells by altering viral surface proteins to recognize only the receptors on cancer cells.

    Viruses could be engineered to attach to the surface receptors on cancer cells to alert the immune system to the presence of cancer.

    Viruses sometimes cause cancer. This is a bad idea.

    Viruses are pathogenic and will infect the host. This treatment will not work.

    Viruses could be used to carry genes exclusively to the normal body cells. These genes could encode proteins that would help destroy the cancer cells.
    Viruses could be engineered to infect only cancer cells by altering viral surface proteins to recognize only the receptors on cancer cells.
  • smiraclelynch
    Answered in Chapter 18-19
    Why are phages useful in treating bacterial infections in humans? (Concept 19.2)


    Because of their host specificity, they only attack bacteria. They do not affect eukaryotic cells.

    Because of their specificity, a phage can be used that will only infect the pathogenic bacteria, leaving helpful bacteria alone.

    Because phages are free to evolve, bacteria are less likely to develop a lasting resistance to them.

    They are not useful, and the practice has been banned in all countries.

    The first three answers are correct.
    The first three answers are correct.