Viruses Flashcards
What type of ecosystems do viruses play a role in?
marine ecosystem
What is a virus?
a noncellular particle that must infect a host cell to reproduce
What does a virion consist of?
nucleic acid (DNA or RNA) contained within a protective protein coat called the capsid
host range
a particular group of species that a virus infects
Viruses take over the infected cell’s ________ and direct the cell to ______ more virus particles.
machinery; produce
Average size of a virus
50-100 nm
What are giant viruses called?
pandora viruses
Three things that virus nucleic acid can be:
- DNA/RNA
- linear or circular
- ds or ss
Name a few genes that the virus genome can encode for
capsomere, envelope protein, polymerase
Capsid
protein coat made of repeating protein subunits called the capsomere; used for protection and packaging of the viral genome
envelope
lipid bilayer that surrounds the capsid and obtained from the host cell membrane (budding)
Enveloped viruses are ____ sensitive to inactivation by ____ or ______________ than nonenveloped viruses.
more; heat; detergents
Spikes
glycoproteins in the envelope
What do spikes help with?
Attachement to/release from the host cell
Four Virus Shapes
- Filamentous/Helical
- Icosahedral
- Complex
- Other
3 characteristics of helical viruses
- vary in length, depending on genome size
- helical symmetry
- include bacteriophages as well as animal viruses
Are viruses included in the binomial nomenclature scheme?
no
3 things classification is based on
- nucleic acid
- morphology
- method of replication
viral species
group of viruses that share the same genetic information and host range
family names end in
-viridae
genus names end is
-virus
What type of names are used for species?
common
How are subspecies designated?
by numbers
3 identification methods
- cytopathic
- sereological
- nucleic acid sequence
2 life cycles for bacteriophage
lystic, and lysogenic
3 life cycles of animal viruses
DNA, RNA, retrovirus
5 steps of lytic cycle
Attachment, Penetration, Biosynthesis, Assembly/maturation, Release
5 steps of lysogenic cycle
attachment, penetration, integration, excision, lytic cycle
6 steps of general life cycle of animal viruses
attachment, penetration, uncoating, biosynthesis, maturation, release
release of enveloped viruses from infected cells
budding
release of nonenveloped viruses from infected cells
lysis, exocytosis
RNA viruses
use an RNA dependent RNA polymerase to transcribe their RNA
DNA virus
uses the host replication machinery
retrovirus
uses reverse transcriptase to copy their genomic sequence into DNA for insertion into the host chromosome
Is influenze A enveloped or nonenveloped?
enveloped
H
hemagglutinin protein; 16 subtypes; attachment to host cell;
N
neuraminidase; 9 subunits; involved in release from host cell
Antigenic Drift
gradual change in surface molecules of virus (spikes)
Why is antigenic drift bad?
host antibodies may not recognize the altered antigens
acute infection
rapid production of virus particles, relatively brief period of disease symptoms, the host immune response rids body of infecting virus
Viroids
Rna molecules that infect plants; NO protein capsid
Are viruses bigger than viroids?
YES
How do viroids replicate?
by host RNA polymerase; weird because it usually requires a DNA template
some viroids have _______ ability
catalytic
Prions
proteins that infect animals with no nucleic acid component
Where do prions come from?
derived from normal cellular proteins
What do prions do?
alter the conformation of normal cellular proteins
How do you get prions? (4)
- inherited
- transmissible through: ingestion
- transplant
- surgical instruments
4 diseases prions can cause:
- Sheep scrapie,
- Mad Cow Disease
- Chronic wasting Disease
- Spongiform encephalopathies
What causes Creutzfeldt-Jakob disease?
prions
What are the symptoms of Creutzfeldt-Jakob disease?
dementia, blindness, impaired muscular coordination, behavioral changes (insomnia, depression)
