Virology intro and history Flashcards
Where did viruses come from?
Viruses are derived from cellular genetic material that has acquired the capacity to exist and function independently*
*except for pox viruses
What is the etymology of the word “virus”?
late 14c., “poisonous substance” (a sense now archaic), from Latin virus “poison, sap of plants, slimy liquid, a potent juice,” from Proto-Italic *weis-o-(s-) “poison,” which is probably from a PIE root *ueis-, perhaps originally meaning “to melt away, to flow,” used of foul or malodorous fluids, but with specialization in some languages to “poisonous fluid” (source also of Sanskrit visam “venom, poison,” visah “poisonous;” Avestan vish- “poison;” Latin viscum “sticky substance, birdlime;” Greek ios “poison,” ixos “mistletoe, birdlime;” Old Church Slavonic višnja “cherry;” Old Irish fi “poison;” Welsh gwy “poison”).
The meaning “agent that causes infectious disease” emerged by 1790s gradually out of the earlier use in reference to venereal disease (by Edward Jenner 1728); the modern scientific use dates to the 1880s. The computer sense is from 1972.
What virus is Louis Pasteur (1885) known for investigating? What vaccine did this result in?
- Rabies
- In July 1885 Louis Pasteur successfully inoculated his untested rabies vaccine on Joseph Meister, a boy who was bitten by a rabid dog. The nine-year-old recovered. Rabies vaccine was the first live attenuated viral vaccine
- Pasteur attenuated the virus by serial “passage and desiccation” to vaccinate humans and animals.
Who discovered the first virus of vertebrates and what virus was it?
- F. A. J. Loeffler and P. Frosch, in 1898, working with Robert Koch
- Foot and Mouth Disease (FMD) virus
- They demonstrated that FMD is caused by such “filterable” agents. They were the first to prove that viruses could infect animals
What is a virus?
- A virus is an infectious particle composed of a protein coat and a nucleic acid core.
- Viruses only replicate inside of a cells.
- Virions can only be observed by an electron microscope.
- Virion is the extracellular and mature form of the virus.
Are viruses micro-organisms? Why/why not?
No.
Viruses are not alive because they have:
- No cellular structure
- No functional organelles
- No protein and nucleic acid capability by themselves
Viruses are dependent on the host cell for survival and replication
obligate intracellular parasites
Why is virology considered a part of biology if viruses are not alive?
Viruses belong to biology because they possess genes, replicate, evolve and are adapted to particular hosts
Once inside a host cell, what does the virus do?
- hijacks the host metabolic and genetic systems to produce:
- viral genome
- viral mRNA
- viral proteins
- –> these are assembled to form progeny virions
What kind of genetic material do viruses contain?
Viruses contain only one kind of nucleic acid, either DNA or RNA
What are the three components of a virus?
- Nucleic Acid: DNA or RNA
- Capsid: protein coat
- Envelope: lipoprotein, acquired by budding through cellular membranes
The capsid and enclosed nucleic acid of a virion constitute the [__________].
The capsid and enclosed nucleic acid of a virion constitute the nucleocapsid.
What are the two types of virion symmetry?
- icosahedral
- helical
What is a capsomer?
Repeating of similar subunits that make us the virion capsid
What are the benefits of icosahedral structural symmetry?
The icosahedron is the optimum solution to the problem of constructing, from repeating subunits, a strong structure enclosing a maximum volume
The capsomers on the faces and edges of icosahedral virions, bond to [five/six] neighbouring capsomers and are called [_____] or [_______]; those at the vertices bond to [five/six] neighbours and are called [_____] or [_______]
The capsomers on the faces and edges of icosahedral virions, bond to six neighbouring capsomers and are called hexon or hexamer; those at the vertices bond to five neighbours and are called penton or pentamer
