General-Structure-Etc. (Ex1) Flashcards
What are viruses? General Features (6)
- non-living entities
- contain nucleic acid genome surrounded by protein coat
- do not possess organelles
- cannot make energy or proteins by themselves
- are obligate intracellular parasites
- cannot multiply by division
What is a virion?
a complete virus particle that consists of an RNA/DNA core with a protein coat
Edward Jenner
- invented vaccinations
- cowpox matter to prevent small pox
Charles Chamberland
- invented the Chamberland filter
- pores smaller than bacteria
Louis Pasteur
- created Rabies vaccine
- infected rabbit brain material into patients
Martinus Beijerinck
- called infectious substance a virus
- Tobacco Mosaic virus
Friedrich Loeffler and Paul Frosch
- discovered cause of foot and mouth disease
Walter Reed
- conqueror of yellow fever
- spread by mosquitoes
Peyton Rous
- isolated first tumor-causing animal virus
- Rous sarcoma virus
Ernst Ruska and Max Knoll
invented electron microscope
Woodruff, Goodpasture, and Burnet
- propagated fowlpoxvirus in embryonated hens eggs
Which are the smallest viruses?
- Porcine circovirus type 1
- Parvoviruses
Which are the largest viruses?
- Pandoravirus
- Poxvirus
What is a capsid?
the protein shell of a virus that encases the viral nucleic acid or genome
- made up of capsomeres
What is the Triangulation number and what is the equation to calculate it?
- describes the relation between the number of pentagons and hexagons of the icosahedron
- the larger the number, the more hexagons relative to pentagons
- T=(h^2 + h)(k + k^2)
What are the functions of the viral envelope?
- facilitates entry into host cells
- helps virus adapt fast and evade host immune system
Describe virus envelope glycoproteins
- anchored in the lipid bilayer by hydrophobic bonds
- transmembrane proteins with large external domain and small cytoplasmic domain
- external (antigens), channel, fusion
Features of Electron Microscopy
- Biological materials need to be stained
- Requires negative staining with electron dense material
- not very detailed
Features of Cryo-Electron Microscopy
- biological specimens in their native environment
What are the functions of the viral capsid?
- structural symmetry of virus particle
- protects viral nucleic acid
- facilitates attachment to receptors on host cell
- transport of viral genome to specific site
- determines antigenicity of virus
Describe the virus envelope matrix proteins
- link the internal nucleocapsid to the envelope
- crucial role in virus assembly
- stabilization of lipid envelope
- recognition site of nucleocapsid at the plasma membrane and mediates encapsidation of nucleoprotein cores into membrane envelope
Positive Sense RNA Virus
- has an infectious genome
- similar to mRNA and can be immediately translated by host cell
Negative Sense RNA Virus
- has non-infectious genome
- complementary to mRNA and must be converted to positive sense before translation
What happens in each of the point mutations?
silent, nonsense, missense
Silent: codes for the same amino acid
Nonsense: codes for a stop codon
Missense: codes for a different amino acid
What happens in recombination?
exchange of nucleotide sequences between different, but closely related, viruses during replication
- involves a single gene segment
What happens in reassortment?
coinfection with two different strains
- segments mixed up in host
- forms reassortment progeny
- only in viruses with multiple gene segments
What are lysins?
hydrolytic enzymes produced by bacteriophages to cleave the host’s cell walls
What is retroviral integrase?
enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cells
What is reverse transcriptase?
enzyme used to generate complementary DNA from an RNA template
What are neuraminidases?
enzymes that cleave glycosidic bonds which allows release of viruses from host cell
What are Defective Interfering Particles?
when the defective virus cannot replicate, but it can interfere with other congeneric mature virions entering the cells
What is a pseudovirion?
- contains non-viral genome within the viral capsid
- looks ordinary but does not replicate
