Virology II

Question 1

How do viruses replicate their genomes?

Answer 1

The viral DNA is replicated by the viral DNA polymerase
Positive sense RNA is from a 5’ to 3’ direction
Negative sense means that the RNA polymerase must replicate it in the opposite direction by making a complementary RNA strand so positive sense
Retroviruses can form DNA from RNA through reverse transcriptase e.g. HIV

Question 2

What is the Baltimore classification?

Answer 2

Viruses are put in different groups dependent on their genome classification

Question 3

What are protein polymerases like?

Answer 3

Polymerase proteins are enzymes that are involved in the catalysis of nucleotides to nucleic acids
Viruses with DNA genomes produce DNA polymerases
Viruses with RNA genomes produce RNA polymerases
Polymerase proteins interacts with nucleic acid in protein-nucleic acid interactions
Structural proteins
Proteins that form the capsid into which nucleic acid is packaged
Proteins interact with one another in protein-protein interactions

Question 4

What is pathogenesis?

Answer 4

As “obligate cellular parasites” viral and cellular proteins shape the intracellular environment to facilitate virus replication or evasion of an immune response
Commonly, changes to intracellular environment that facilitate virus replication or evasion of an immune response lead to disease; pathogenesis

Question 5

How are viruses and cancer linked?

Answer 5

As cells divide, they go through the ‘cell cycle’. During the cell cycle the cell produces factors that a virus might need
An example of this is the production of nucleotides that can be used by viral polymerases to make new viral genomes
Some viruses produce proteins that ensure the cell continually goes through the cell cycle
Cancer can be defined as uncontrolled cell division
Thus, viruses can cause cancer by causing uncontrolled cell division that benefits their replication

Question 6

How does virus pathogenesis cause immunodeficiency?

Answer 6

Viruses must evade immune responses
Some immune responses are mediated by specific cells of the immune system
These immune cells recognise and kill cells infected by virus
To evade this type of immune response, some viruses replicate in the immune cells whose function is to recognise and kill infected cells
Replication in immune cells hides the virus from immune cells and inhibits immune cell function
Inhibition of immune cell function allows other pathogens to replicate in virus infected hosts and thus disease occurs