Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
20 Cards in this Set
- Front
- Back
|
How would you define a virus
|
An obligate intracellular parasite that contains a genome, capsid, maybe an envelope, and multiplies by taking over the synthetic machinery.
They are host specific to bacteria, animal cells, and plant cells |
|
|
3 types of viruses by shape:
|
Helical Viruses (shape of capsid) - Resemble long rods that can be rigid/flexible. Some are surrounded by an envelope with or without spikes. Ex; Ebola & Rabies
Polyhedral Viruses (many sided/equilateral triangles) - Capsid is in the shape of an icosahedron (capsomeres form equilateral triangles). Ex; Polio & Adenovirus Complex Viruses - Often bacterial viruses that have capsids w/ additional structures attached |
|
|
what is a capsid made of?
|
it's a protein coat composed of capsomeres
|
|
|
what's a viral envelope?
|
envelope made of lipids, carbohydrates, and proteins all taken from the host cell. may have spikes.
|
|
|
what's the difference between lytic and lysogenic growth?
|
lytic: attach, penetrate, synthesize, assemble, burst (lyse) cell and release virions.
lysogenic: attach, penetrate, Phage DNA integrates w/i the bacterial chromosome by recombination, becoming a PROPHAGE → Lysogenic bacterium reproduces normally → Occasionally, prophage may excise from bacterial chromosome by another recombination event, initiating a lytic cycle |
|
|
what can't happen after a prophage has been triggered and gone lytic?
|
no more prophages are produced in the infected cell - a bunch of virions go out, and these will not go lysogenic.
|
|
|
what can't happen to a cell infected by a prophage?
|
One a cell is lysogenic, it can no longer be infected by the same phage type
|
|
|
compare and contract animal viruses and bacteriophages
|
"life" cycle similar but the big difference comes from the fact that one affects prokaryotes and the other eukaryotes.
attachment different: bacteriophages grab cell wall proteins with their tail fibers, viruses bond to plasma membrane penetration different: animal viruses insert the whole capsid (via phagocytosis or membrane fusion) while phages insert just genetic material.i |
|
|
what is the shape of a polyhedral virus?
|
icosahedron - capsomeres form equilateral triangles.
|
|
|
what are "t-even bacteriophages" and what "life cycle" do they generally follow?
|
bacteriophages are named T1, t2, etc. t-even ones tend to follow lytic cycle.
|
|
|
what do viruses use to breakdown host dna?
|
exonucleases
|
|
|
what are sigma factors?
|
proteins used by viruses to modify host polymerases to transcribe 'late' proteins.
|
|
|
about how much time does the lytic cycle take?
|
25 minutes after which the cell is ruptured and new virions released.
|
|
|
what is burst time/burst size?
|
burst time-time elapsed between attachment of virion to cell and the lysis and release of "viral progeny."
|
|
|
what is eclipse period?
|
phase in viral growth curve where the virus is no longer an infectious particle - just genetic material within a host cell.
|
|
|
what's an example of a "temperate phage?" what is it?
|
it doesn't always cause the host cell to lyse. Bacteriophage lambda - phage dna enters host cell and forms a circle which can be transcribed as is for a lytic cycle OR become integrated w/ host genome as a lysogenic cycle.
|
|
|
how do lysogenic viruses avoid the lytic cycle? what is it called when the phage dna "pops out" of the host genome and initiates lytic cycle.
|
phage genes can produce REPRESSOR PROTEINS.
when dna pops out (can be triggered by stress, UV light, etc), it's called "lysogenic induction." |
|
|
what is transduction? contrast generalized and specialized transduction.
|
transduction - transfer of bacterial DNA from one cell to another by a bacteriophage.
Generalized: host dna that got broken down when LYTIC BACTERIOPHAGE infected the cell gets packaged into phage capsid. Specialized: Since LYSOGENIC BACTERIOPHAGE dna got incorporated into host DNA, it can pull adjacent bits of genome with it. |
|
|
what do you call a virus with "tumor capability"? how does that cause cancer?
|
oncogenic viruses alter "oncogenes" in the host cell genome. cells lose the ability to die (apoptosis), and form tumor-like masses
|
|
|
What are Prions (describe structure)
|
PROTEINACIOUS INFECTIOUS PARTICLES - proteins folded abnormally. they enter brain cells from infectious tissue, and grab onto normal proteins causing THEM to fold, now they roam around folding more proteins until the cells die, releasing more of these folded proteins.
|
