11.4 Structure of Viruses Flashcards
How do viruses grow and divide?
They don’t. They merely replicate using the machinery of a host cell
Why must all viruses make mRNA?
So that it can be translated into protein
What characterises a non-enveloped virus?
No cellular envelope; contained entirely by viral proteins
What characterises an enveloped virus?
- Pick up part of host cell membrane as they leave the cell
- Viral proteins studded in membrane
What is the structure that surrounds RNA/DNA in enveloped viruses?
Nucleocapsids (made of viral protein)
Do viruses contain DNA or RNA?
Either; never both
What is the fundamental function of viral enzymes?
Make new genomes or mRNA
What types of enzymes can be in a virus?
- RNA dependent RNA polymerase
- RNA dependent DNA polymerase (reverse transcriptase)
- Protease
- Integrase
Which types of cells are best for viral infection studies? Why?
- Primary cells
- Mimic the organ from which they were taken (have a finite lifespan, though, which is bad logistically)
Which types of cells are used in viral replication studies? What characterises them, and why are they used?
- Immortal cell lines
- Genetically altered to be able to replicate indefinitely
What are the main microscopic indicators that tell us that viruses are replicating in a cell/culture?
- Cytopathic effect (CPE), leading to cell death
- Syncytia formation (large cells with many nuclei)
What is one common way in which CPE can be used to tell us how many viral infections are in a sample?
Plaque assay -> each infection radiates outward, creating a small gap in the crystal violet stain
In the absence of a cytopathic effect, how else can we determine the extent of viral infection?
-Immunofluorescence microscopy (fluorescent antibodies bind to viral proteins)
- Genetically engineering viruses contain fluorescent proteins
- qPCR
