BIOL 121 Flashcards
Define “virus”
A simple, miniscule, infections, obligate intracellular parasite comprising of genetic material and surrounded by a capsid or envelope
Why do viruses have so few genes?
Because they are obligate parasites and they dont need to code for complex machinery to reproduce themselves
How large are viruses
usually around 20-300nm (very small)
How large are Giant Viruses
around 750nm so large enough to be seen with a light microscope and have larger genomes
What do you call transmission viruses and replication viruses
Extracellular virions (transmission) and intracellular virions (replication)
How do virus populations change over time
they have an eclipse period of silence and then a burst of rapid growth
How are viruses studied
Electron microscopy, X-ray crystallography, Cryo-EM, NMR
what are the subunits of capsids
capsomers
What is the combination of capsids and nucleic acid
nucleocapsid
What shapes are viruses
Helical, polyhedral and Binal (complex/irregular)
what is the function of the capsid
protets the nucleic acid and aids its transmission
Do viruses need an envelope
No they can be enveloped and naked
What is the structure of a bacteriophase
They have a head, sheath, base plate and tail fibres
What is the replication cycle of bacteriophages
Adsorption, penetration, replication, maturation, release and reinfection
What is a bacteriophage that kills its host called and what is one that isn’t
Lytic phages kill their hosts and temperate/lysogenic phages dont
What is a bacteria carrying prophages called
lysogens
What are phages used for
disinfectants and antibiotics for hard to kill bacteria as well as vaccine vectors
How does phenogenetic analysis help in virus outbreaks
allows for the genome to quickly be identified by comparison to similar genetic sequence viruses
What do all viruses have in common
The viral genome must make mRNA that can be read by host ribosomes
Is mRNA +ssRNA or -ssRNA
always +ssRNA
How many types of viruses are there in baltimore system and what are they
7 -
1 dsDNA
2 gaped dsDNA
3 ssDNA
4 dsRNA
5 +ssRNA
6 -ssRNA
7 +ssRNA with DNA intermediate
What ways can viruses infect cells
1 Transformation into tumor cell via virus
2 Lysis (death of cell & release of virus
3 persistant infection (slow release without cell death)
4 latent infection (virus present but delays lysis until later triggered)
How do viruses find cells to infect
They have to attatch via a receptor (excluding fungal and plant viruses)
How do viruses enter the cell
1) injection of nuceic acid
2) fusion of envelope with host virus
3) Endocytosis
What does the virus do in the cell
synthesises viral proteins using host ribosomes and replicating the viral genetic material
How does the virus exit the cell
the virus capsid pushes against the membrane and wraps iteslf in membrane containing viral glycoproteins (produced by host ribosomes using viral genes) and naked viruses exit via lysis
What are Viroids
Very small infectious agent that are NOT viruses with very small circular ssRNA, naked, resistant to proteases and only infect plants.
The replication mechanism is unknown
What are prions
They are small infectious proteinaceous particles (only protein no genetic material).
How is rabies spread
via saliva through bites (mostly dogs)
What are the two forms of rabies
Furious and dumb (furious regular form but dumb can occur and make the dog just appear sleepy)
How is Mpox transmitted
Animal to human occurs via bites and scratches as well as meat from infected animals
Human to human contact is via direct skin contact with lesions (only infectious after symptoms appear) and contact with contaminated fomities such as bedding
How is Mpox treated
Vaccines are the main treatment (one antiviral very recently approved)
What are obelisks
Viroid like elements (slightly larger) first found in human oral and stool metatranscriptomic data
what are prion diseases called
spongiform encephalopathies
How are prions caused
The accumulation of misfolded proteins causing other proteins to misfold as well
What diseases are caused by prions
Scrapie - degenrative fatal CNS disease in sheep
BSE - mad cow disease (erratic behaviour) (classical BSE can be transferred into humans causing Creutzfeld-jacob disease)
Kuru - “trembling” passed on from cannibalism
Creutzfeld-Jacob disease - loss of ability to think and move properly usually fatal (4 forms Sporadic, familial/inherited, Variant (meat) and Latrogenic (by accident from surgery)
