Virology Flashcards
What can viruses infect?
- plants
- animals
- bacteria
- fungi
- other viruses
A virus that infects bacteria won’t infect any other thing
What are the differences between deasd and alive viruses?
Dead
1. inert
2. no cell compounds
3. no metabolism
4. no autonomy
Alive
1. Nucleic aicd
2. proteins
3. mutate
4. grow and multiple
5. react
Inert= onactive when not in a host
No autonomy= cannot survive on their own
True or false
All viruses have a nucleic acid and a protein coat
True
What is the structure of a virus?
- Nucleic acid
- encodes virus genes
- protein coat
* protective
* enzymatic - envelope (lipid bilayer)
* matrix protein
Spikes attach to receptor sites on host cells. Phages attach by tail fibers.
Enveloped viruses have a lipid bilayer obtained from a host cell.
Enveloped viruses are more susceptible to disinfectant because damage to the envelope does not allow them to infect
What are the 3 shapes of viruses?
- Icosahedral
- helical
- complex
What is the description of a icosahedral shape?
20 flat triangles
What is the description of a helical shape?
capsomeres arranged in helix
What is the description of a complex shape?
- phage
- icosahedral nucleocapsid (head)
- helical protein (tail)
What are bacteriophages?
- infect bacteria
* lytic
* temperate
* filamentous
bacteriophages enter and leave the bacteria via the F pilus
exit the host by lysing the cell
What is lytic?
lyse the host cells and then end of infection
What is temperate?
lytic or lysogenic
What is filamentous?
- rod shaped
- requries an F-pilus
What is horizontal gene transfer in bacteriophages?
Transduction
* generalized
* specialized
What is generalized horizontal gene transfer?
- Bacterial DNA that has been degraded can accidently packaged with new phage heads
- Some viruses contain only fragmented bacterial DNA, these viruses cannot drive replication, but can incorporate into newly infected cell
What is specialized horizontal gene transfer?
- Bacterial DNA is excised with virus DNA when going from lysogenic to lytic
- When incorporated into Phage it is defective, can also be incorporated into targets DNA
What is a bacteriophage?
a virus that infects bacteria
What is a capsomere?
proteinaceous subunit of a capsid
some capsomeres are composed of only a single type of protein, whereas others are composed of several different kinds of proteins.
What is present in a viruses extracellular state?
virions have capsids-protein coats that provide both protection for viral nucleic acid and a means by which many viruses attach to their hosts’ cells.
What is a capsid made of?
capsomeres
What is a nucleocapsid?
nucleic acid surrounded by a capsid
What are the three basic shapes of virions?
Helical, polyhedral, and complex
True or False?
All viruses lack cell membranes
True
True or False
Animal viruses have an envelope similar in composition to a cell membrane surrounding their capsids
True
What is a virion called when it lacks an envelope?
non-enveloped or naked
What are the 5 steps of the animal virus infection cycle?
- attachment (absorption)
- genome entry
- synthesis
- assembly
- release
What happens in a lytic replication cycle?
- Attachment of the virion to the host cell
- Entry of the virion or its genome into the host cell
- Synthesis of new nucleic acids and viral proteins by the host cell’s enzymes and ribosomes
- Assembly of new virions within the host cell
- Release of the new virions from the host cell
Where are most DNA viruses located?
Nucleus
Where do most RNA viruses develop?
solely in cytoplasm
During viral replication, how are enveloped viruses released?
by budding
can result in persistent infections
How are naked viruses released?
exocytosis or lysis
What are acute infections?
- Rapid onset; short duration
- Burst of virions released from infected host cell
- Immune system gradually eliminates virus
What are persistent infections?
- continue for years or lifetime
- may or may not have symptoms
Can be chronic or latent
What is a chronic infection?
continuous production of low levels of virus particles
carriers may lack symptoms, but still transmit the virus
What is a latent infection?
viral genome remains silent in host cell; can reactivate to cause productive infection
What is a prion?
are proteinaceous infectious agents
* Linked to slow, fatal human diseases; animal diseases
* Usually transmitted only within a species
* Composed solely of protein; no nucleic acids
What are the characteristics of prions?
Cellular PrP
* made by all mammals
* normal, functional structure has α-helices
Prion PrP
* Disease-causing form has β-pleated sheets
* Prion P r P causes cellular P r P to refold into prion P r P
True or False
Normal sterilization procedures do not deactivate prions
True
How are prions destroyed?
Prions destroyed by incineration or autoclaving in concentrated sodium hydroxide
