Virology

Question 1

what is a virus?

Answer 1

obligate intracellular parasite

Question 2

what does a virus depend on its host for?

Answer 2

• Small molecules ie nucleotides, lipids, AAs and carbs
• Energy
• Macromolecular synthesis of the virus component parts

Question 3

function of the virion?

Answer 3

to deliver the viral genome into a host cell where it can be replicated

Question 4

what are the hypothesis’ of virus origin?

Answer 4

The progressive or escape hypothesis- rose from genetic elements that gained the ability to move
The regressive of reduction hypothesis-remnants of cellular organisms
The virus first hypothesis-predate or coevolved with their current hosts

Question 5

are viruses more likely to infect eukaryotes or prokaryotes?

Answer 5

eukaryotes

Question 6

what do virions contain?

Answer 6

The viral genome- DNA or RNA
Capsid - structural proteins and enzymes
Attachment spike proteins

Question 7

what do the attachment spike proteins do?

Answer 7

target virus to specific host cells

Question 8

what are spike proteins?

Answer 8

Proteins on surface of virion often glycoproteins which bind with cell surface molecules

Question 9

what do viroid’s only contain?

Answer 9

RNA

Question 10

What do prions only contain?

Answer 10

Protein

Question 11

what is the viral envelope made of?

Answer 11

Lipid bilayer and Viral glycoproteins - involved in attachment of virus to receptor on susceptible cell

Question 12

what is the nucleocapsid?

Answer 12

The full assembly of genome and capsid protein that lies at the core of virus particles

Question 13

what are the two types of nucleocapsid symmetry?

Answer 13

Helical symmetry or icosahedral symmetry

Question 14

what is SARS CoV 2 composed of?

Answer 14

Positive sense RNA virus with long single stranded RNA genome of 29 kilobases

Question 15

what are the virus life cycle stages?

Answer 15

Adsorption
Penetration
Uncoating
Replication and gene expression
Assembly
Maturation
Release

Question 16

If the cell does not die, how does the virus alter the nature and/or behaviour of the cell?

Answer 16

Altered cell phenotype
Altered cell physiology
Altered genetic material of the host cell

Question 17

what are lytic infections?

Answer 17

Lytic cycles both kill and solubilize host bacteria

Play a major role in carbon recycling within the environment

Question 18

what are lysogenic infections?

Answer 18

phage replicate with cells without producing bacteriophage virion particles

Question 19

what are virulent phage?

Answer 19

Phage that lyse cells

Question 20

what is lysogeny?

Answer 20

when some phage infect the bacterial cell, they replicate with (rather than within) the bacterial cell and only cause lysis under appropriate environmental conditions

Question 21

what are the phage that take part in lysogeny called?

Answer 21

temperate phage or prophage eg lambda or Mu

Question 22

what does the establishment of lysogeny depends upon at a cellular level?

Answer 22

The genotypes of both the phage and of the host bacterial cells
The physiological status of the bacterial host cell
Phage concentration

Question 23

what factors influence temperate phage bacterial host interactions in nature?

Answer 23

Biological factors such as cell development and community dynamics
environmental factors such as those that cause stress and environmental variation

Question 24

how do viruses make us sick?

Answer 24

1. alter the physiology of tissue

2. cause inflammation

Question 25

what is encephalitis?

Answer 25

inflammation of the brain

Question 26

what is viral hepatitis?

Answer 26

inflammation of the liver

Question 27

how are HAV and HEV transmitted?

Answer 27

via the faecal/ oral route as contaminants of drinking water or food

Question 28

how are HCV and HBV transmitted?

Answer 28

via blood- sexually or maternally

Question 29

what are the types of diagnostic tests for viral infections?

Answer 29

direct, indirect or by serology

Question 30

how are direct diagnostic tests carried out?

Answer 30

Electron microscopy to detect morphology or tissue changes.
PCR to detect virus nucleic acid.
Use of antibodies to specifically detect parts of virus proteins

Question 31

When are indirect diagnostic tests carried out?

Answer 31

To look for cytopathic effects (will the cells shrink, bleb, lyse, burst) when a clinical sample is used to infected monolayers of cells in the laboratory

Question 32

what do serology tests detect?

Answer 32

past infection, usually by ELISA