Lecture 2 Flashcards
What are the steps in viral replication (6)
- Attachment
- Penetration
- Uncoating
- Replication of viral proteins and nucleic acid - eclipse phase
- Assembly of the viral proteins and packaging of the nucleic acids
- Release of virions
What is attachment
Ligands/receptors sites on the surface on the surface of the visions bind to receptors on the cell surface
How is the initial binding of attachment done
Electrostatic forces
How does attachment occur
when there is a specific affinity exists between the cell and the virus
What determines TROPISM of viruses
Presence or absence of sites
How does a reversible bond work
A loose contact between cell membrane and virus which depend upon the maintenance of the electrostatic forces produced by the concentration of electrolytes
What is the reversible bond dependent on
Temperature
How does the irreversible bond work
Late stage of the process which become temperature dependent. The virus is now protected from antibodies
What are the 2 mechanisms of penetration
- Endocytosis
2. Fusion
How is the process of uncoating brought about
Lysosomes
How does the Eclipse phase occur
- DNA is transcribed to viral mRNA which is translated to viral proteins
- The gnome of positive strand RNA viruses may function as a mRNA
What type of proteins make up a virion
Structural protein
What functions do non-structural proteins have
Protease and transcriptase activity or transport of other proteins
Where is viral DNA transcribed
Nucleus
How are helical capsids assembled
Helical capsids usually assemble around strands of nucleic acids
How are icosahedral capsids assembled
as empty sheets and filled with nucleic acids
How are complex viruses assembled
progressively assembled to form the complete virion
How are DNA viruses assembled
in the nucleus
How are RNA viruses assembled
in the cytoplasm
How are naked viruses released
Lysed
How are enveloped viruses released
Bud through host membranes
What do most viruses inhibit
Protein synthesis
How can Eukaryotic host translation be inhibited (3)
- Inhibition of host cell mRNA from the nucleus
- Differential degradation of host cell mRNA
- Blockage of host cell mRNA
What can picornaviruses shut down
Host ribosome translation
What does the eclipse phase mean
Disappearing phase
Can you see the virus in the eclipse phase
No, it is where transcription and translation is occurring
What is syncytial formation
Fusion of cell membranes - giant cel formation
What are inclusion bodies
Dark areas with a halo around it
