Lecture 17: Intro To Virology Flashcards
(38 cards)
What therefore must viruses be to endure nature?
Infectious
Why are viruses not living organisms?
They cannot produce energy or proteins independently of a host cell
What must viruses be able to do
Use cell processes
Encode any required proteins not provided by the host. E.g. Special enzymes like reverse transcriptase, RNA dependent RNA polymerase etc
What sort of agents are viruses? (Due to their small size)
Filterable agents. - I.e. they cannot be removed by microfilters
What can viral genomes be?
Either DNA or RNA but NOT both
What morphologies do viruses have?
Naked capsid or
Envelope morphology
How are viral components different to Bacterial components?
They are assembled (self assembly)
They do not replicate by division
Viruses don’t grow in size, they grow in number
How can viruses be classified?
structure, biochemical characteristic Disease Means of transmission Host cell Tissue or organ Members of particular family Location of first isolation
How are viruses classified by structure?
Structure classification by size, morphology, nucleic acid,
E.g. Picornavirus (means small RNA )
How can viruses be classified by their biochemical characterstics?
By their structure, mode of replication
E.g. Togavirus (means mantle envelope),
retrovirus (which converts RNA to DNA )
How can viruses be classified by their disease?
Classified by the disease they cause
E.g. Encephalitis virus, hepatitis virus, poxvirus
How can viruses be classified by their means of transmission?
E.g. Arbovirus means spread by insects
How can viruses be classified by the host cell?
By the type of host they infect.
Animal, plant, bacteriae, e.g. Bacteriophage
How can viruses be classified by tissue or organ?
Classification by the tissue or organ they infect,
e.g. Adenovirus and enterovirus.
How can viruses be classified by members of a particular family?
E.g. Papovavirus (including papilloma, polyoma, vacuolating virus)
How can viruses be classified by their location of their first isolation?
E.g. Coxsackievirus found in cocksackie, NY
List the human DNA viruses in order of increasing size
Parvovirus Papovavirus Adenovirus Herpesvirus Poxvirus
Name the human RNA viruses in order of increasing size
Picornavirus Reovirus Togavirus Coronavirus Orthomyxavirus Rhabdovirus Paramyxovirus
List the viruses that infect bacteria in order of increasing size
Bacteriophage MS2
Bacteriophage M13
Bacteriophage T2
What is a virus that infects plants?
Tobacco mosaic virus
Name the main components of a virus
Glycoproteins Bilipid layer Nucleic acid Capsid Capsomere (Envelope)
What are the features of a naked capsid virus
Environmentally stable to temperature, acid, proteases, detergents and drying
Released from cell by lysis
Can be spread easily (e.g. By dust, hand to hand contact)
Can dry out BUT still contain infectivity
Can survive adverse conditions of the gut
Can be resistant to poor sewage treatment
What are features of enveloped viruses?
Environmentally labile
Disrupted by acid, detergent, drying and heat
Released from host cell by budding OR cell lysis
Must remain wet
Cannot survive in GI tract
Spreads in large droplets, body fluids (blood, saliva, breast milk, transplants, blood transfusion)
Does not necessarily need to kill the cell to spread
What are latent viral infections?
Persistent infections
Virus does not reproduce hence no clinical symptoms
Virus can occasionally activate and produce symptoms
E.g. Herpes, chickenpox, HIV
