Understanding Retroviruses and Reverse Transcription
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Questions and Answers

What is the diameter of the spherical enveloped particle of retroviruses?

  • ~80-100nm (correct)
  • ~10-20nm
  • ~200-250nm
  • ~50-60nm

    • Which proteins are derived from the pol gene in retroviruses?

  • MA (matrix), CA (capsid), NC (nucleocapsid)
  • SU (external surface protein, also called gp120) and TM (transmembrane protein, also called gp24)
  • MA (matrix), CA (capsid), NC (nucleocapsid)
  • PR (protease), RT (reverse transcriptase), IN (integrase) (correct)

    • What is the function of the gag gene in retroviruses?

  • Encoding of envelope proteins: SU (external surface protein, also called gp120) and TM (transmembrane protein, also called gp24)
  • Involvement in genome replication and integration
  • Cleavage of polyprotein into mature proteins
  • Production of group-specific antigen proteins: MA (matrix), CA (capsid), NC (nucleocapsid) (correct)

    • What is the initial step in the unique replication cycle of retroviruses?

    <p>Reverse transcription to produce a DNA copy of the RNA genome</p> Signup and view all the answers

    What is the role of reverse transcriptase in retroviruses?

    <p>To produce a DNA copy of the RNA genome</p> Signup and view all the answers

    Where does the DNA enter after being made from the ssRNA genome by viral enzyme integrase?

    <p>Nucleus with the viral enzyme integrase</p> Signup and view all the answers

    What is bound to genomic RNA by base pairing with primer binding sequences downstream of U5?

    <p>A specific cellular tRNA</p> Signup and view all the answers

    What are the two subfamilies into which retroviruses were reclassified?

    <p>Orthoretrovirinae and Spumaretrovirinae subfamilies</p> Signup and view all the answers

    What is the function of Ppt in retroviruses?

    <p>It is used during reverse transcription</p> Signup and view all the answers

    What is the main basis for the tropism of retroviruses?

    <p>Interaction of SU with cellular receptor</p> Signup and view all the answers

    What is the role of ribonuclease H (RNAse H) in reverse transcription?

    <p>Specifically degrades the RNA part of the RNA:DNA hybrid</p> Signup and view all the answers

    What facilitates the DNA polymerase activity during reverse transcription?

    <p>Virus-associated cellular tRNA</p> Signup and view all the answers

    Which type of genome does HIV possess?

    <p>+ssRNA (positive sense single-stranded RNA)</p> Signup and view all the answers

    What causes depletion of CD4+ T cells in HIV-infected individuals?

    <p>All of the above</p> Signup and view all the answers

    What is the main basis for the tropism of retroviruses?

    <p>Interaction of SU with cellular receptor</p> Signup and view all the answers

    What is the diameter of the spherical enveloped particle of retroviruses?

    <p>~100nm</p> Signup and view all the answers

    What facilitates the DNA polymerase activity during reverse transcription?

    <p>Virus-associated cellular tRNA</p> Signup and view all the answers

    What is the role of ribonuclease H (RNAse H) in reverse transcription?

    <p>Specifically degrades the RNA part of the RNA:DNA hybrid</p> Signup and view all the answers

    What is bound to genomic RNA by base pairing with primer binding sequences downstream of U5?

    <p>Virus-associated cellular tRNA</p> Signup and view all the answers

    Which proteins are derived from the pol gene in retroviruses?

    <p>Reverse transcriptase and integrase</p> Signup and view all the answers

    What causes depletion of CD4+ T cells in HIV-infected individuals?

    <p>HIV replicating in and killing lymphocytes and macrophages</p> Signup and view all the answers

    What is the function of Ppt in retroviruses?

    <p>Ppt is polypurine tract used during reverse transcription</p> Signup and view all the answers

    What is the function of the env gene in retroviruses?

    <p>Codes for external surface protein and transmembrane protein</p> Signup and view all the answers

    What is the role of the U3 region in retroviruses?

    <p>It is a splice site</p> Signup and view all the answers

    What is the function of the protease (PR) protein in retroviruses?

    <p>Cleaves the polyprotein into mature proteins</p> Signup and view all the answers

    What is the specific cellular component bound to genomic RNA by base pairing with primer binding sequences (PBS) downstream of U5?

    <p>Transfer RNA (tRNA)</p> Signup and view all the answers

    What is the primary function of reverse transcriptase (RT) in retroviruses?

    <p>Catalyzes the synthesis of DNA from RNA template</p> Signup and view all the answers

    What is the role of nucleocapsid protein in retroviruses?

    <p>Packages viral RNA genome with nucleic acid</p> Signup and view all the answers

    What is the function of integrase (IN) enzyme in retroviruses?

    <p>Facilitates integration of viral DNA into host cell DNA</p> Signup and view all the answers

    Which proteins are derived from the gag gene in retroviruses?

    <p>Matrix, Capsid, Nucleocapsid proteins</p> Signup and view all the answers

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