Virus Genome Flashcards
What are the five stages of viral infection?
- Virus enters the cell
- DNA of the virus is uncoated
- Viral DNA is translated and transcribed
- Newly synthesised viral proteins and newly replicated viral DNA assemble to form new viral particles
- New virus particles leave the cell
What must a cell be in order for a virus to enter?
Susceptible and permissive
What are susceptible cells?
Cells in which viral entry is allowed by having the right cell attachment factors
- Receptors and coreceptors
What molecules act as receptors and coreceptors on susceptible cells?
Proteins and glyco-conjugates
Different cells display different ________ and different viruses recognise different __________
Markers
Receptors
What are permissive cells?
Cells in which viral replication is supported = the right structural and non-structural proteins are present
What is tropism?
The ability of a virus to replicate inside a given cell
What are the two ways in which viruses may enter a cell?
Endocytic pathway
Fusion (non-endocytic) pathway
What is the endocytic pathway?
Clathrin mediated endocytosis and penetration
What is the fusion pathway?
Viral envelope fuses with the cellular envelope and the virus enters the cell
How do viruses transport themselves around the cell?
On intracellular pathways
When are attempts to stop viral action made?
When the intracellular pathway the virus uses is known
What is produced when viral DNA is translated and transcribed?
Viral RNA and viral proteins
How are new viral proteins and DNA produced?
Using the host cells ‘synthesis machinery’
- Hosts ribosomes
- Hosts enzymes
- Hosts tRNA
What raw materials naturally present in host cells are used in the production of viral DNA and proteins?
Nucleotides
Amino acids
Energy
What are non-structural proteins?
Building tools
- Enzymes
When are non-structural proteins required and in what quantities are they required?
Required immediately upon infection in small quantities
Where are non-structural proteins required?
Only in infected cells
Will non-structural proteins become part of the virus?
No
What are structural proteins?
Building bricks
- Proteins
When are structural proteins required and in what quantity are they required?
Only required after the genome is replicated in large quantities
Do structural proteins become part of the virus?
Yes
What are structural proteins required to form?
Progeny particles
What does the viral genome code for?
Structural and non-structural proteins
DNA or RNA (not both)
Is the viral genome single or double stranded?
Either depending on whether it is composed of DNA or RNA
What is baltimore classification?
Viruses are classified into one of seven groups depending on how viral genomes are converted into mRNA
What are the features of positive sense RNA?
5’ to 3’
Start and stop codons
Open reading frame
Can be translated and transcribed immediately
What are the features of negative sense RNA?
Compliment of positive sense strand
Cannot be translated immediately
A complementary strand must be produced before transcription and translation occur
Why is it hard for viral DNA to replicate in neurons?
Because neurons do not replicate and divide and therefore do not have ‘synthesis machinery’ for the virus to use
Viruses have different tropisms, what does this mean?
Different viruses target different organelles in cells
What helps to classify viruses?
Viral genomes
What are adenoviruses?
Viruses that infect linings within the body
How do adenoviruses enter cells?
- Receptor binding
- Entry in clathrin coated vesicles
- Transport to early endosomes
- Endosomal acidification and lysis
- Cytosol penetration
- Travel to nuclear pore complex via microtubules
