11.5 Viral Life Cycles and Replication Flashcards
Do viruses infect random cells?
No. They attach to specific receptor molecules on the surface of cells that express them.
Is viral entry active or passive?
Active
What is the role of viral entry?
Transfer the genome inside the cell for protein manufacture for viral replication
Is one receptor always used for viral entry?
No; can be more than one
Describe three different ways in which a virus can enter a cell
- Uncoat at plasma membrane to release genome into cell
- Release genome directly into nucleus
- Intracellular vesicles
Do all viruses use the same cellular attachment receptors?
- No
- In general, each viruses has its own specific attachment receptors
How can receptors specificity of viruses help localise a viral infection?
- Different receptors are expressed in different organs/tissues
- A cell must express all necessary receptors to be infected by a virus
- Therefore, there may be a small number of areas in which a virus could infect (e.g. Hep C)
Where do most RNA viruses replicate their genome in a host cell?
Cytoplasm
Where do most DNA viruses replicate their genome in a host cell?
Nucleus
How are non-enveloped viruses released?
- Spontaneous assembly of viral proteins following translation
- Release from host cell
How are enveloped viruses released from a host cell?
- VIruses embed themselves in “endoplasmic” or “golgi”
- Upon budding out, viruses picks up viral proteins and host lipid bilayer
Why don’t viruses with positive strand need an RdRp?
Since RNA is already positive sense, the existing RNA can already act as mRNA for replication.
Why do dsRNA and negative strand RNA need an RdRp?
RNA cannot act as mRNA, and so an enzyme is needed to create mRNA for transcription, translation, and replication
How much of the viral RNA genome must be copied to produce another virus?
- All of it, no loss of sequence
In which direction (in terms of ends) is the new RNA strand synthesised?
New strand is synthesised from 5’ to 3’ end
