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Viruses
What are Viruses?
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Virus – _______________ of nucleic acid, protein, and in some cases lipids
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Not ___________
Do NOT exhibit _______________________________________
Can only reproduce when inside a _________________
Cannot maintain _______________________
Very simply a virus is __________________________ enclosed in a ______________________
Viral Structure
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Viruses contain ______ or ______ but ________________
DNA or RNA is surrounded by a protein coat call a ____________
– Proteins in the capsid give the virus ________________________
– Shape of the virus causes the virus to be ____________________ (can only infect a certain type of cell)
Some viruses are enclosed by a protective _________________________
Some viruses have ____________ to help attach to the host cell
Virus vs Cell
Characteristic
Virus
Cell
Structure
Reproduction
Genetic Code
Growth & Development
Obtain & Use Energy
Response to Environment
Change Over Time
Viruses & Disease
**Remember ALL viruses are parasitic which means they require a living host and they cause harm to that host**
Bacteriophages
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A virus that _____________________ is known as a ______________________ or ____________
Bacteriophages are used for ______________________ in genetics
– Ex: to “program” bacteria to produce insulin for the treatment of diabetes
Retroviruses
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Group of viruses that contain ________ as their ________________________________
Retroviruses have a complicated reproductive cycle because they must carry out
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Contain a special enzyme call __________________________________
– This enzyme helps a cell transcribe __________________________
Examples: _________ and feline leukemia
Fighting Viral Infections
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Antiviral drugs work by _____________________ with the genetic material or the ______________________________
– This will __________________ the virus from ______________________ in the host cell
Examples: tamiflu, acyclovir
Benefits of Viruses - Not all viruses are bad!
– __________________ for viral diseases are made from _________________________ of the virus
– A weaker virus is capable of stimulating an ______________________ and creating _________________, but not
causing illness
Viral Hosts
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Remember that a host is necessary for viral replication
_____________ host range = infect _______________ species
– Ex: Swine flu and rabies
______________ host range = infect ____________ species
____________________ host range = infect ____________________ of one species
– Ex: Human cold virus attack cells of the respiratory system
Viral Cycles
There are three initial steps that are common to all viral infections:
1. Virus _____________ to the cell ____________________ of the host cell
2. Trick cell into allowing it inside
3. Virus releases its __________________________ (DNA or RNA) into the host cell
- ____________________ – Viral DNA is ____________
- Transcription – Viral _______ is converted into ________
- Translated – _______________________ are made from the RNA
Once inside the host cell, there are two ways that a virus can take over and reproduce:
1. Lytic Infection
2. Lysogenic Infection
Lytic Infection
1. ________________________ to the cell
2. Penetration (__________________) of viral DNA or RNA
3. Virus ____________________________ to copy viral DNA and make _____________________
4. New viruses ______________________ and mature
5. Cell lyses (_______________) and releases the new viruses to attack other cells
6. Results in ______________ of the host cell
Lysogenic Infection
1. Virus ________________ to host and ___________________ DNA
2. Viral DNA joins host DNA forming a ______________________
3. Viral DNA _________________ along with host DNA
4. Remain __________________ for a period (generations)
5. Eventually viral DNA __________ host cell and _____________________________