Viruses Flashcards
What are viruses?
Obligate intracellular parasites
What does obligate intracellular mean?
In order to replicate they require a live host
Why are viruses distinguishable from other infectious agents?
Because they are small and are therefore filterable
What human illnesses are viruses responsible for?
Influenza
Measles
Diarrhoea and vomiting
AIDS
What plant illnesses are viruses responsible for?
Tobacco mosaic virus
Tomato spotted wilt virus
What livestock illnesses are viruses responsible for?
Foot and mouth
SARS = severe acute respiratory syndrome
Bluetongue virus
Where do new human viruses often originate from?
Viruses that are present in animals
What are the benefits of viruses?
Can be used for biological control = control wild animal populations
Used for cancer treatment
What boundaries do viruses cross?
Species boundaries
What are zoonose?
Infectious diseases caused by bacteria, viruses and parasites that spread between animal species
Name two common zoonose viruses?
Yellow fever
Dengue
How much of our DNA is made of genetic material evolved from viruses?
5-8% = acquired through infection of germ cells
How big are viruses?
20-300nm = too small to be seen using a light microscope
Do viruses have a simple or complex structure?
Simple
Do viruses have a big or a small genome?
Small
Do viruses metabolise?
No
How is genetic information encoded in viruses?
On one linear or circular piece of RNA or DNA (never both) surrounded by a protein coating
How do viruses multiply in host cells?
Using the hosts synthesising machinery
Name three methods of culturing animal viruses.
Embryonated eggs = influenza strands can be grown in chicken eggs
Cell cultures
Living animals
How can we visualise virus replication?
- Monolayer of cells poured onto a plate
- Cells are exposed to a virus
- Cells which have been infected with the virus can be seen
What are cells infected with viruses called?
Plaques
Why do antibiotics not work against viruses?
Because viruses do not metabolise
What must drugs aimed at eliminating viruses be?
Specific to the virus however must no affect the host cell - must stop viral multiplication
What is an attenuated vaccine?
Weakened form of the virus
What is an inactivated vaccine?
A dead form of the virus
What is a subunt vaccine?
Stimulates the immune system
What is a conjugate vaccine?
A combination of antigen and protein to aid immune system recognition
What is a nucleic acid vaccine?
Injected DNA
How can viruses be prevented from spreading?
- Break transmission routes = condoms
- More people vaccinated
- Stop slaughter of infected animals
- Restricted movement of animals with viral infections
- Control vectors = eliminate mosquito’s
