32 Questions
What is the polypurine tract (PPT) used for in retroviruses?
Facilitates reverse transcription
Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?
Ribonuclease H (RNAse H)
What is the main basis for retroviral tropism?
Interaction of SU with cellular receptor
What is the role of cellular tRNA molecules packaged in retroviral virions?
Act as primers for reverse transcription
What is the type of genome present in HIV virions?
+ssRNA (positive sense single-stranded RNA)
What is the primary target of HIV replication and killing within the host?
Lymphocytes and macrophages (CD4+ cells)
What characterizes the acute infection phase of HIV?
Flu-like symptoms and significant drop in CD4+ cells
What is the significance of lentivirus as a term for HIV?
It reflects the slow progression of the disease
What is the diameter of the spherical enveloped particle of retroviruses?
~80-100nm
Which enzyme is responsible for generating DNA copies of RNA genomes in retroviruses?
Reverse transcriptase
What is the function of the viral enzyme integrase in retrovirus replication?
Directs integration of viral DNA into host cell DNA
Which gene encodes proteins involved in genome replication and integration in retroviruses?
Pol (polymerase)
What is the function of the Gag proteins in retroviruses?
(matrix), CA (capsid), NC (nucleocapsid)
What is the role of the primer binding sequences (PBS) in retrovirus replication?
Binding to a specific cellular tRNA to initiate reverse transcription
What are the unique regions adjacent to R in retroviral genomic RNA?
U5 (untranslated 5’, 80-200 nt) and U3 (untranslated 3’, 240-1200 nt)
What is the function of the specific cellular tRNA bound to genomic RNA in retroviruses?
Serves as a primer for reverse transcription
What is the diameter of the spherical enveloped particle of HIV?
100nm
Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?
Ribonuclease H (RNAse H)
What is the primary target of HIV replication and killing within the host?
Lymphocytes and macrophages
Which type of genome is present in HIV virions?
+ssRNA (positive sense single-stranded RNA)
What is the significance of lentivirus as a term for HIV?
It refers to the slow progression of the disease caused by HIV
What characterizes the acute infection phase of HIV?
Flu-like symptoms and significant drop in CD4+ cells
What is the role of cellular tRNA molecules packaged in retroviral virions?
Act as primers for reverse transcription
What is polypurine tract (PPT) used for in retroviruses?
Used during reverse transcription to initiate DNA synthesis
What is the diameter of the spherical enveloped particle of retroviruses?
~80-100nm
What is the primary function of the Pol (polymerase) proteins in retroviruses?
Involved in genome replication and integration
What is the role of the primer binding sequences (PBS) in retrovirus replication?
Binding to a specific cellular tRNA
What is the function of the specific cellular tRNA bound to genomic RNA in retroviruses?
Serving as a primer for reverse transcription
Which enzyme in retroviruses specifically degrades the RNA part of the RNA:DNA hybrid?
RNase H
What characterizes the acute infection phase of HIV?
High levels of viral replication and rapid CD4+ T cell depletion
What is the main basis for retroviral tropism?
Interaction between viral envelope proteins and host cell receptors
What is the significance of lentivirus as a term for HIV?
It reflects HIV's ability to cause slow, chronic infections with long incubation periods.
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.
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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