Retrovirus and Reverse Transcription
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Questions and Answers

What is the polypurine tract (PPT) used for in retroviruses?

  • Triggers conformational shift in the SU protein
  • Promotes viral integration into the cellular genome
  • Facilitates reverse transcription (correct)
  • Initiates viral entry into the host cell

    • Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?

  • DNA polymerase
  • Virus-associated cellular tRNA
  • Ribonuclease H (RNAse H) (correct)
  • RNA-dependent DNA polymerase

    • What is the main basis for retroviral tropism?

  • Conformational shift in TM protein
  • Presence of PPT in the viral genome
  • Interaction of SU with cellular receptor (correct)
  • Integration into cellular genome

    • What is the role of cellular tRNA molecules packaged in retroviral virions?

    <p>Act as primers for reverse transcription</p> Signup and view all the answers

    What is the type of genome present in HIV virions?

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

    What is the primary target of HIV replication and killing within the host?

    <p>Lymphocytes and macrophages (CD4+ cells)</p> Signup and view all the answers

    What characterizes the acute infection phase of HIV?

    <p>Flu-like symptoms and significant drop in CD4+ cells</p> Signup and view all the answers

    What is the significance of lentivirus as a term for HIV?

    <p>It reflects the slow progression of the disease</p> Signup and view all the answers

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

    <p>~80-100nm</p> Signup and view all the answers

    Which enzyme is responsible for generating DNA copies of RNA genomes in retroviruses?

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

    What is the function of the viral enzyme integrase in retrovirus replication?

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

    Which gene encodes proteins involved in genome replication and integration in retroviruses?

    <p>Pol (polymerase)</p> Signup and view all the answers

    What is the function of the Gag proteins in retroviruses?

    <p>(matrix), CA (capsid), NC (nucleocapsid)</p> Signup and view all the answers

    What is the role of the primer binding sequences (PBS) in retrovirus replication?

    <p>Binding to a specific cellular tRNA to initiate reverse transcription</p> Signup and view all the answers

    What are the unique regions adjacent to R in retroviral genomic RNA?

    <p>U5 (untranslated 5’, 80-200 nt) and U3 (untranslated 3’, 240-1200 nt)</p> Signup and view all the answers

    What is the function of the specific cellular tRNA bound to genomic RNA in retroviruses?

    <p>Serves as a primer for reverse transcription</p> Signup and view all the answers

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

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

    Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?

    <p>Ribonuclease H (RNAse H)</p> Signup and view all the answers

    What is the primary target of HIV replication and killing within the host?

    <p>Lymphocytes and macrophages</p> Signup and view all the answers

    Which type of genome is present in HIV virions?

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

    What is the significance of lentivirus as a term for HIV?

    <p>It refers to the slow progression of the disease caused by HIV</p> Signup and view all the answers

    What characterizes the acute infection phase of HIV?

    <p>Flu-like symptoms and significant drop in CD4+ cells</p> Signup and view all the answers

    What is the role of cellular tRNA molecules packaged in retroviral virions?

    <p>Act as primers for reverse transcription</p> Signup and view all the answers

    What is polypurine tract (PPT) used for in retroviruses?

    <p>Used during reverse transcription to initiate DNA synthesis</p> Signup and view all the answers

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

    <p>~80-100nm</p> Signup and view all the answers

    What is the primary function of the Pol (polymerase) proteins in retroviruses?

    <p>Involved in genome replication and integration</p> Signup and view all the answers

    What is the role of the primer binding sequences (PBS) in retrovirus replication?

    <p>Binding to a specific cellular tRNA</p> Signup and view all the answers

    What is the function of the specific cellular tRNA bound to genomic RNA in retroviruses?

    <p>Serving as a primer for reverse transcription</p> Signup and view all the answers

    Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?

    <p>RNase H</p> Signup and view all the answers

    What characterizes the acute infection phase of HIV?

    <p>High levels of viral replication and rapid CD4+ T cell depletion</p> Signup and view all the answers

    What is the main basis for retroviral tropism?

    <p>Interaction between viral envelope proteins and host cell receptors</p> Signup and view all the answers

    What is the significance of lentivirus as a term for HIV?

    <p>It reflects HIV's ability to cause slow, chronic infections with long incubation periods.</p> Signup and view all the answers

    Study Notes

    Retroviral Structure and Function

    • The polypurine tract (PPT) is used as a primer for DNA synthesis in retroviruses.
    • Retroviral genomes are composed of RNA.
    • The genome present in HIV virions is diploid, meaning it consists of two identical copies of the genome.

    Enzymes in Retroviral Replication

    • The enzyme reverse transcriptase is responsible for generating DNA copies of RNA genomes in retroviruses.
    • The enzyme RNase H specifically degrades the RNA part of the RNA:DNA hybrid.
    • The enzyme integrase is responsible for integrating the viral DNA into the host genome.

    Retroviral Replication

    • The primary target of HIV replication and killing within the host is CD4+ T cells.
    • The acute infection phase of HIV is characterized by a rapid increase in viral replication and a subsequent decline in CD4+ T cells.
    • The Gag proteins are involved in the formation of the viral capsid and are necessary for genome replication.
    • The primer binding sequences (PBS) are necessary for the binding of tRNA to the viral genome.
    • The specific cellular tRNA bound to genomic RNA acts as a primer for DNA synthesis.

    Retroviral Tropism

    • The main basis for retroviral tropism is the specific interaction between the viral envelope protein and the host cell receptor.

    Retroviral Classification

    • The term "lentivirus" is used to describe HIV because it causes a slow, progressive disease.
    • The diameter of the spherical enveloped particle of retroviruses, including HIV, is approximately 100-120 nm.

    Retroviral Genes

    • The Pol gene encodes proteins involved in genome replication and integration.
    • The Gag gene encodes proteins involved in the formation of the viral capsid.

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    Test your knowledge about retroviruses and the process of reverse transcription, which involves making a DNA copy of an RNA molecule. Learn about their structure, composition, and classification into subfamilies and genera.

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