Section 1 Flashcards
Viruses are incapable of replication outside of a host cell therefore they are ______ ______
Obligate Symbionts
Viruses ________ (do or don’t) have a single evolutionary origin
DO NOT
Viruses have ______ genome complexities and effects on host
Varying
Virus transmission can be via ______ _____ or other mechanisms
Extracellular virions
Viruses can exist as _______ by having evolutionary overlap with other types of genetic information
Hybrids
Phage M2 infects __ ____ and has ______ as its genome
Ecoli
+ve sense
Pandoravirus infects _____ and has _______ as its genome
dsDNA
most. viruses are transmitted between cells as ______
Virions
A simple virion consists of _________ surrounded by a ____________
A nucleic acid genome, A capsid (protective protein layer)
A virions nucleic acid genome + thecapsid (protective protein layer) = _________
Nucleocapsid
Some viruses have more than a capsid and contain a lipid ______ as well
envelope
The virion is (usually) ________ inside the host to release the genome
Disassembled
Virus is Latin for _______
Poison
Viruses were first identified as an infectious agent In 1890s by Martinus Beijerinck studying the disease of ______ ______
tobacco plants (tobacco mosaic virus TMV)
Before the discovery of viruses, tulips were sold at very expensive prices because they had _____ ______ due to tulip mosaic virus
distinctive patterning
Right after TMV was discovered in plants, ____ ____ _____ ______ was discovered in animals as caused by a virus
Food and mouth disease (virus FMDV)
First cancer causing virus discovered in the early 1900s as ____ _____ ______ (because they took filters from a tutor and injected it into other people and it made another tumor)
Rous Sarcoma Virus
First bacteriophage discovered in 1915 by _____ _____ and then in 1917 by Canadian ______ ______
Frederick Twort
Canadian Felix d’Herelle (by accident)
Felix d’Herelle was studying shigella virus causing dysentery in children but his bacteria kept dying. THEREFORE, he accidentally discovered a type of viruses (bacteriophages) and successfully used it to treat Dysentery as ______ ______
Phage therapy
1- Why is the study of viruses an important tool for human medicine? (5 things)
- Enzymes for molecular biology (cloning, protein manipulation etc)
-CRSIPER gene editing*, **
-Gene therapy
-Phage therapy
-Cancer therapy
*transplantation of pig heart into human after genetically modifying it
**pig example in the notes that had its PERVs inactivated to make LOW FAT pigs
2- Viruses are important as strong selective forces on the ______ of the _____ by moving genes from cell to cell (viral and cellular genes)
Evolution of hosts
3- Viruses are important as the most ______ entities on earth
Abundant
4- Viruses contain most of the ____ _____ on Earth
Genetic Diversity
Importance of Viruses (4 things)
- for medical and research reasons
- for evolution of hosts
- most abundant on earth
- most diverse on earth
____% of the human genome is made of viruses (endogenous retroviruses) (ex. development of placenta is done by a protein that came from a retrovirus)
5%
Viruses infecting bacteria are a frequent cause of different strains and they confer the benefits of ________ and cons of ________
Benefits: carry useful genes, may provide protection of infection by other virus
Cons: time bombs that may become activated or go into lytic replication to kill the cell –> if single celled = :’(
old time vaccination was called “Variolation” as _____ ______ developed the practice in 1790 to incubate cowpox to prevent smallpox
Edward Jenner
______-________ is when immunity to one virus confers protection against a different closely related virus (ex cowpox and smallpox)
Cross-protection
Vaccines eventually developed better to become _____ versions of a virus to still infect but with a milder disease
Attenuated
Attenuated Vaccine was first developed against _____ by _____ ______
rabies by Lewis Pasteur
***cow infected with rabies BRAIN —-> mouse (spinal cord) —–> another mouse = milder and attenuated rabies
Viruses were finally able to be grown in ________ in the 1950 which was a major advancement for vaccine development
In culture
________ virus has particles bigger than most bacteria and genomes larger than most bacteria
(broke the ‘small’ virus stereotype
recently discovered ______ is even bigger
Mimiviruses
Pandoravirus even bigger
Patrick Forterre argued that a virion is not a virus RATHER the infected host is the virus (aka:_______)
virocell
“a virus is like a seed is to a plant”
Key points in the life of a virus are
1-
2-
3-
Getting in (attachment, entry, uncoating?)
Doing stuff inside (transcription, translation, replication assembly)
Getting out (exiting)
Function of early genes expressed:
Function of late genes expressed:
early= expression of genes that ALLOW replication to happen
late= replication, assembly, packaging
A virus getting into the cell is only possible if the cell has the right receptor making it __________
Susceptible
A virus replicating inside a cell is one possible if cell has the correct things the virus needs _________
Permissive
eukaryotic viruses and even phages show _______ (use different parts of cell for different activities)
Compartmentalization
Viruses get out either by _____ or _____
Budding or lysis
(some plant viruses even come out without particles covering them, just the genomic material moves)
Transmission of viruses between hosts can be complex requiring different ______
Vectors
Classification of viruses is most commonly done using the _________
Baltimore Scheme (7 categories by genome)
Viruses can be grouped together based on _____, ______, _____ or _______
Host, Structure, Genome, Transmission mode
Look up Baltimore classes of genomes ***
The authority controlling virus taxonomy is _______ ______ on ______ of ________ (group of volunteers)
International Committee on Taxonomy of Viruses (ICTV)
The 8 levels of taxonomy
Realm, Kingdom, Phylum, Class, Order, Family, Genus, Species (>1000 species)
Names of taxonomic viruses are printed in ______ and first letters of names are _______
italics, capitalized
_____ viruses require a helper virus to replicate
Satellite viruses
_____ replicate independently but do not code for any proteins
viroids
The three hypothesis about origin of viruses
1- viruses are the “last universal common ancestor” (LUCA)
2- viruses are derived from cells and are genetically reduced parasitic entities
3- viruses evolved from cells but escaped from cellular control after cells evolved into 3 domains
Technologies that help us see viruses
electron microscopy, cryogenic-electron microscopy 3D, x-ray crystallography
When viruses are composes of copies of multiple subunits It is good for _______
if a capsid has the same subunits it has _______
genomic economy
symmetry
if viruses can assemble spontaneously it is called ______
self-assembly
Virus ______ = the geometry of its outline
shape
Virus ______= the rotational and translation relationships that describe the shape
symmetry
1- Viral Structure is called _________ = a shape with 20 triangular faces, with >2x rotational axis needing 3 copies of a protein to make on face
icosahedral symmetry
using math to define symmetry of capsids is called ______ _______ as viruses get bigger and more complicated
triangulation number
2- Viral structure is called ______ _____= fairly common with similar advantages to icosahedral
Helical symmetry
Viruses with envelopes often get them from the _____ ______ through budding
cell membrane
RG1:
Little to no risk, work on open bench
RG 2+3
particular mask to prevent inhalation
glasses to avoid splashes in eye
gloves and lab coat
work in biological safety cabinet
RG3
compete isolation in suits
