Micro 2 test 2 Flashcards
Acellular
they are not a cell
Size Range
200-300 nanometers (variola)
18-30 nanometers (polio and rhinoviruses)
morphology
helical (rod); cubic (geometric)
No combination
RNA and DNA
Surrounded by a
capsid
what are capsids made of
capsomeres
What do viruses require for replication?
a living cell
If a virus reproduces without killing a cell it is
a persistant infection
If a virus kills a cell it is
lytic
Viruses show specificity how?
by species e.g. polio->primates but not chicken
What is tropism?
affinity for target tissue
What are interferons?
a family of eukaryotic cell protiens made and released by host cells in response to the presence of viruses
What do interferons allow?
communication between cells to trigger protective defenses
What is the least favored method for cultivating viruses?
Animals (because they may have other viruses)
infection and replication
5 categories
attachment penetration uncoating biochemical replication assembly and maturation
attachment happens because of
ionic bonds and receptors
penetration happens because of
membrane fusion
uncoating happens where
intracellular
assembly and maturation happens where?
in nucleus and cytoplasm (DNA) cytoplasm only (RNA)
How do you harvest viruses?
2 ways
- Harvest from liquid growth medium which overlays cell culture
- differential centrifugation (used for purity)
What are the assays? (6)
- electron microscope
- titration
- plaque assay
- lethal dose 50% (LD-50)
- Hemagglutination (HA)
- ELISA (enzyme-linked immunosorbant assay)
What is electron microscope used for?
observe/examine the size structure of various viruses
what is titration used for?
to determine titer of the virus in the sample
What is plaque assay used for?
to quantitate viable virus particles derived from both bacteria and animals
What do plaques on a lawn of a cell represent?
a virus infection
Each plaque represents
one virus particle
What is plaque assay analogous to?
viable cell count in bacteriology
virus induced plaques serve as a tool for _______
enumeration
LD-50 assay measures what?
the highest dilution of a virus that is required to kill 50% of the experimental animals
What does LD-50 not give?
a specific virus particle number
What does LD-50 provide?
an idea of the relative strength of the preparation (when comparing two or more samples)
Hemagglutination does what?
provides a means of detecting the viruses prescence and quantitating their numbers by (causing RBC clumping)
ELISA uses what to test?
blood serum (antibodies)
ELISA is ________ and _______ based.
colored and enzyme
ELISA is particularly useful for
HIV testing
HIV testing relies on what two assays?
- ELISA (introductory)
2. Western Blot (confirmatory)
What assay requires a serial dilution of the virus preparation?
hemagglutination
Which assay requires incubation of the virus preparation?
hemagglutination
What are the steps of lytic infection?
- infection
- infected
- bacteriophage maturation
- bacteriophage maturation
- lysis
What step of lysogeny has induction?
3—->4 (e.g. temperature)
What step of lysogeny has transduction?
4
What step of lysogeny has lysis?
5
Are RNA viruses permanent?
no
T or F
RNA viruses integrate into cells.
F
T or F
RNA viruses replicate in the nucleus.
F
T or F
RNA viruses are single stranded.
T
What are the 6 common RNA virus families?
- PICORNAVIRIDAE
- RETROVIRIDAE
- TOGAVIRADAE
- RHABDOVIRIDAE
- PARAMYXOVIRIDAE
- ORTHOMYXOVIRIDAE
What are some examples of picornaviridae?
polio, ECHO, Coxackie, HAV, Rhino (common cold)
What are some examples of retroviridae?
animal tumor and leukemia, HIV, HTLV-1 & HTLV-2