Virology 2

Question 1

What is the configuration of viral genomes?

What are the features of RNA and DNA?

Answer 1

Single-stranded RNA (ssRNA)

Double-stranded RNA (dsRNA)

Single-stranded DNA (ssDNA)

Double-stranded RNA (dsDNA)

Double-stranded genomes have complementary base pairing

RNA genomes can be linear and segmented i.e. more than one RNA per capsid

DNA genomes can be linear or circular.

Genomes can be encode information (genes) in
positive or negative sense; 5’-3’ or 3’-5’ respectively.

Question 2

How do viruses replicate DNA?

Answer 2

The central dogma produces DNA (DNA polymerase), RNA polymerase to produce your RNA strand and translation produces the protein

Question 3

What is positive and negative sense RNA

Answer 3

Positive is organised from the 5’-3’ direction and negative is organised from the 3’-5’ direction. This involves RNA replication. It is RNA dependent and requires RNA polymerase

You also have reverse transcriptase from positive sense to DNA.

Question 4

Describe virus proteins - polymerase

Answer 4

Viruses with DNA genomes produce DNA polymerases

Viruses with RNA genomes produce RNA polymerases

Polymerase proteins interact with nucleic acid in protein-nucleic acid interactions.

Question 5

Describe Virus proteins - structural proteins

Answer 5

Proteins that form the capsid into which nucleic acid is packaged.

Proteins interact with one another in protein-protein interactions.

Question 6

What is Pathogenesis?

Answer 6

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 the intracellular environment that facilitate virus replication or evasion of an immune response lead to disease; pathogenesis.

Question 7

Describe Virus pathogenesis - Cancer

Answer 7

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 8

Give an example of a virus that affects the cell cycle?

Answer 8

Human Papillomavirus (HPV) proteins E6 and E7 “remove the brakes” of the cell cycle

Question 9

Describe Virus pathogenesis - Immunodeficiency

Answer 9

Viruses must evade immune responses. Some immune responses are mediated by specific cells of the immune system. These immune cells recognize and kill cells infected by virus.

To evade this type of immune response, some viruses replicate in the immune cells whose function is to recognize 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.