Virology Flashcards
Shapes and sizes of viruses
Range in size from 20nm to 120nm
Icosahedral
Rotavirus
Filamentous
Spherical
3 principles viruses abide by
Must be infectious to endure in nature
Can’t make own energy or proteins
Viral components must self-assemble
Definition of Nucleocapsid
The genome (whether DNA or RNA) contained within a protein capsule
Definition of virion and how this differs for naked viruses vs enveloped viruses
Virion = infective viral particle
Naked virus = Nucleocapsid is the virion
Enveloped virus virion = Nucleocapsid and envelope
Characteristics of influenza virus
Spherical enveloped virus
The following glycoproteins:
H = hemagglutinin receptor (has a role in attachment of the virus to the cell and fusion
N = neuroaminidase
Both of the above are susceptible to antigenic drift (mutation) and shift (recombination) which gives rise to many strains
Characteristics of norovirus
Icosahedral and naked
+ strand RNA
Affects mostly in winter through contact, contaminated food or water or surface
What are the consequences of being enveloped or naked
Naked are more stable in the environment stress and spread more easily eg rotavirus and norovirus
Enveloped viruses must stay wet to remain infectious and very sensitive to detergents
Spread through large droplets and does not need to kill cell to spread (can just bud)
Eg HIV, Ebola, influenza, COVID
Viral genomes code for which 3 classes of proteins
Proteins for progeny viral practices
Enzymes for genome replication
Proteins to interfere with host immune defence
Stages of the infectious productive cycle
Attachment to receptors
Penetration
Uncoating
Viral genome into host cell
New genome/protein synthesis
Assembly of new particles
Release
What are the two ways viruses can penetrate into the cell
1) membrane fusion at the cell surface by enveloped viruses as have similar composition of membrane
2) entry by endocytosis mostly by naked viruses
- strand ss RNA viruses
Are all enveloped
Examples: influenza, mumps, measles, rabies and Ebola
Carry enzymes that facilitate replication
Life cycle is not usually associated with the nucleus and progeny viruses are released by budding
Positive strand ss RNA or ds RNA virus
Ss = poliovirus, dengue and hep C, COVID
Ds = rotaviruses
Process is very similar to negative rna viruses
What is burst size
Yield of infectious virus/cell
Retroviruses
Eg HIV
Uses reverse transcriptase to convert RNA to DNA which is then integrated into the hosts genome and then transcribed and translated to produce viral proteins that are released by budding
DNA viruses
Eg herpes viruses (herpes simplex, EBV)
Uses normal cellular functions of host cell and compartments
DNA transcription and translation and replication
Genetic material stays in cell and is reactivated by stress and UV light (herpes)
