Virology: Replication and Pathogenesis

Question 1

What is the eclipse phase of virus replication?

Answer 1

The time between cell infection and the start of virus production

Question 2

What is transcription and where does it occur?

Answer 2

Transcription is the production of mRNA from a genome template and it occurs in the cytoplasm

Question 3

What is translation and where does it occur?

Answer 3

Production of proteins from RNA
Occurs in the cytoplasm

Question 4

What are the 5 steps of virus infection in a cell?

Answer 4

1. Entry
2. Protein Synthesis
3. Genome replication
4. Particle assembly
5. Exit and Release

Question 5

What do reverse transcriptase viruses need to do to ‘fit’ into the central dogma?

Answer 5

They need to produce DNA

Question 6

Which enzyme is a ‘virus-only’ enzyme?

Answer 6

RNA-dependent-RNA-polymerase
as normal cells would not need to create any more RNA

Question 7

What are some of the methods a virus can use to enter the cell?

Answer 7

• Endocytosis
• Fusion with the plasma membrane
• Cell to cell transport

Question 8

What occurs after the virus has entered the cell?

Answer 8

The virus capsid is uncoated
genomic content is released into the cytoplasm

Question 9

What are the two types of viral proteins produced during transcription and translation

Answer 9

Structural and non-structural

Question 10

What is the function of the structural viral proteins?

Answer 10

• To make more virions
• Can also help out with replication

Question 11

What is the function of non-structural viral proteins?

Answer 11

• Viral factory proteins
• intefere with the host proteins
• Counterract the immune response

Question 12

How does viral replication in the nucleus occur?

Answer 12

1. Virus crosses into the cytosol
2. Releases its genome
3. genome is used to transcribe mRNA
4. mRNA leaves the nucleus and proteins are generated i the cytoplasm
5. proteins re-enter the nucleus
6. genomes + proteins combine to make the virions
7. virus is then released through the cell membrane

Question 13

How does viral replication in the cytoplasm occur?

Answer 13

1. everything is made and assembled in the cytoplasm (genome + proteins)
2. virus is released

Question 14

What two enzymes are required for succesful virus replication?

Answer 14

• enzyme that synthesises mRNA for protein synthesis
• enzyme that replicates the genome

Question 15

What are the options for the virus to obtain enzymes?

Answer 15

• Use host enzymes
• enzymes are brought as part of structural proteins
• enzymes are synthesised as part of protein synthesis

Question 16

Why cant you produce mRNA using a non-structural protein?

Answer 16

Because protein synthesis is required to make non-structural proteins (and you need mRNA for protein synthesis)

Question 17

What are some of the positives of virus replication in the nucleus?

Answer 17

• May be able to use host enzymes for replication, transcription and modification
• the latency is easier to establish

Question 18

What are some of the negatives of virus replication in the nucleus?

Answer 18

• They need to cross the nucleus membrane
• This could trigger apoptosis

Question 19

What are three different ways that a virus can exit the host cell?

Answer 19

• Lysis (causes consequence to the cell)
• Budding- production of an envelope (they require part of the cell membrane)
• Exocytosis