Virology Flashcards
what is a virus?
obligate intracellular parasite
what does a virus depend on its host for?
- Small molecules ie nucleotides, lipids, AAs and carbs
- Energy
- Macromolecular synthesis of the virus component parts
function of the virion?
to deliver the viral genome into a host cell where it can be replicated
what are the hypothesis’ of virus origin?
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
are viruses more likely to infect eukaryotes or prokaryotes?
eukaryotes
what do virions contain?
The viral genome- DNA or RNA
Capsid - structural proteins and enzymes
Attachment spike proteins
what do the attachment spike proteins do?
target virus to specific host cells
what are spike proteins?
Proteins on surface of virion often glycoproteins which bind with cell surface molecules
what do viroid’s only contain?
RNA
What do prions only contain?
Protein
what is the viral envelope made of?
Lipid bilayer and Viral glycoproteins - involved in attachment of virus to receptor on susceptible cell
what is the nucleocapsid?
The full assembly of genome and capsid protein that lies at the core of virus particles
what are the two types of nucleocapsid symmetry?
Helical symmetry or icosahedral symmetry
what is SARS CoV 2 composed of?
Positive sense RNA virus with long single stranded RNA genome of 29 kilobases
what are the virus life cycle stages?
Adsorption Penetration Uncoating Replication and gene expression Assembly Maturation Release
If the cell does not die, how does the virus alter the nature and/or behaviour of the cell?
Altered cell phenotype
Altered cell physiology
Altered genetic material of the host cell
what are lytic infections?
Lytic cycles both kill and solubilize host bacteria
Play a major role in carbon recycling within the environment
what are lysogenic infections?
phage replicate with cells without producing bacteriophage virion particles
what are virulent phage?
Phage that lyse cells
what is lysogeny?
when some phage infect the bacterial cell, they replicate with (rather than within) the bacterial cell and only cause lysis under appropriate environmental conditions
what are the phage that take part in lysogeny called?
temperate phage or prophage eg lambda or Mu
what does the establishment of lysogeny depends upon at a cellular level?
The genotypes of both the phage and of the host bacterial cells
The physiological status of the bacterial host cell
Phage concentration
what factors influence temperate phage bacterial host interactions in nature?
Biological factors such as cell development and community dynamics
environmental factors such as those that cause stress and environmental variation
how do viruses make us sick?
- alter the physiology of tissue
2. cause inflammation
what is encephalitis?
inflammation of the brain
what is viral hepatitis?
inflammation of the liver
how are HAV and HEV transmitted?
via the faecal/ oral route as contaminants of drinking water or food
how are HCV and HBV transmitted?
via blood- sexually or maternally
what are the types of diagnostic tests for viral infections?
direct, indirect or by serology
how are direct diagnostic tests carried out?
Electron microscopy to detect morphology or tissue changes.
PCR to detect virus nucleic acid.
Use of antibodies to specifically detect parts of virus proteins
When are indirect diagnostic tests carried out?
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
what do serology tests detect?
past infection, usually by ELISA
