Viruses 1 Flashcards
Describe the “one step viral growth cycle”
What are the stages in viral replication?
Describe a bacteriophage life cycle
What’s the significance of viral tropism and hosts?
What are the routes of viral transmission?
Describe viral attachment
The interaction between a virus and its target cell begins with attachment of the virus particle to specific receptors on the cell
- Attachment is a critical step as a determinant of target selection by many viruses
- Requires viral attachment protein and cellular receptors
What are the major viral attachment proteins and receptors?
What are the steps in penetration and uncoating of enveloped viruses?
- Fusion
Virus glycoproteins attach to host cell receptors, envelope-membrane fusion occurs, capsid enters, is uncoated and virus is released, e.g. Herpesvirus, Paramyxovirus, HIV - Endocytosis and acidification
Host cell cytoplasmic membrane wraps around virus and brings it inside, the capsid is uncoated and the viral genome is released into the host cell, e.g. influenza virus
What are the steps in penetration and uncoating in non-enveloped viruses ?
- Direct entry across plasma membrane
Virus attaches to host cell receptors, sinks into cell membrane, and injects its genome through a pore into the cell, e.g. poliovirus - Endocytosis
Host cell cytoplasmic membrane wraps around virus and brings it inside, the capsid is uncoated and the viral genome is released into the host cell, e.g. parvovirus
What occurs during viral replication?
Uncoating of the viral genome leads to the first step of viral replication, i.e., expression of mRNA (transcription)
- Translation of mRNA generates the so called “early proteins” which often include synthesis of viral DNA or RNA polymerase and other proteins which play an important role in viral replication
- Viral genome replication leads to complementary strand synthesis and additional templates using nucleic acids
- Late mRNA synthesis generates “late proteins” (structural proteins) which participate in the formation of the viral capsomeres
• Capsid formation follows a self-assembly mechanism in most of the cases
➢ some viruses may use chaperones to fold the capsomeres
Describe viral assembly and release
What are the consequences of viral infection?
What are the general patterns of viral infection?
What’s the importance of understanding the viral genome?
Understanding viral genomes means understanding:
➢ Baltimore classification and the phylogenetic relationship between viruses
➢ Modes of genome replication and viral propagations
➢ Opportunities for anti-viral treatment and host immunity
One convergent point for all viruses is that they all need to go through mRNA (+ve) strand synthesis to produce proteins.
➢ Positive (+ve) nucleic acid (DNA or RNA) is the gene coding strand (or the actual gene sequence)
➢ Negative (-ve) nucleic acid (DNA or RNA) is the complementary strand to the gene coding mRNA (the template strand)
what are the characteristics of viral genome?
Contrast positive and negative strands of viral genes
How does the viral replication stack up with the central dogma of biology?
What are the three ways of producing viral proteins with single function?
What are the atypical viruses and virus-like agents?
Describe the spontaneous rate of transmission of prions
