006 How Viruses Multiply

Question 1

What are the 4 steps of the viral replication cycle of a non-enveloped virus??

Answer 1

Attachment and fusion
Eclipse stage
Maturation
Release

Question 2

What occurs during the virus replication cycle?

Answer 2

When viruses attach and fuse into the cell, it is disassembled so the infectious units per cell drop to nearly 0. Usually nothing happens at first because virus takes longer time to grow compared to bacteria. During maturation, cell associated viruses (virus inclusion bodies) begin to replicate raptly. Once it reaches its limit, it is released as cell free virus.

Question 3

Which type of virus can be detected intracellularly and which type can be detected extracellularly?

Answer 3

Unenveloped viruses can be detected intracellularly whilst enveloped viruses can only be detected extracellularly.

Question 4

Is the influenza virus enveloped or unenveloped?

Answer 4

Enveloped

Question 5

Is the polio virus enveloped or unenveloped?

Answer 5

Unenveloped

Question 6

Where can you find the sialiac acid end that haemagglutin binds to?

Answer 6

On the oligosaccharide on the glycoprotein receptor

Question 7

How many virions do viruses produce per infected cell?

Answer 7

1000

Question 8

What is the baltimore classification, and what do all groups lead to?

Answer 8

Classifies virus into their genome groups, but all groups lead to the mRNA which will be translated. This is the equivalent of its -ve sense.

Question 9

How does point mutation occur in viruses?

Answer 9

RNA polymerase does not proof read, leading to mistakes occuring.

Question 10

How does HIV replicate?

Answer 10

Trimer envelop 3 gp 120 subunits bind to CD4 on t receptor. This exposes a co-receptor binding site. Once it is bound to co-receptors, changes in gp41 pull the 2 phospholipid membranes together. Peptide is released into the cell. Reverse transcriptase transcribes viral RNA into DNA. Ribonuclease stops transcription and alllows it to enter the nucleus. Integrase integrates the viral DNA into host DNA by covalent bonds. When the cell is active, proviral DNA is transcribed into mRNA. Viral genome buds out of the cell and could remain latent. Otherwise it will be transcribed and protease will cleave it to form a p24 capsid. This exits the cell and infects other cells.

Question 11

What genome does polio virus contain?

Answer 11

+RNA

Question 12

What genome does influenza contain?

Answer 12

-RNA

Question 13

What genome does the adenovirus contain?

Answer 13

dsDNA

Question 14

What genome do rotavirus contain?

Answer 14

dsRNA

Question 15

What genome does HIV contain?

Answer 15

RNA+