1. Arianna K. Olivia J. Willow G.
Virus Structure

2. Overview What is a virus? Characteristics of a virus
Viral Reproduction 
RNA Viruses
Lytic infections
Lytic Cycle vs. Lysogenic Cycle

3. What is a Virus?
 particles made of proteins, nucleic acids, and sometimes lipids
non-living organisms
crystalize unlike organisms that are living AK

4. How do they differ from Each other?
Specific to one cell: plant, animal, etc.
Size: large, complex or small and simple
Some have additional membranes AK

5. Structures Within a Virus
Capsid: protein surrounding virus
Capsids bind to receptor proteins on cell
DNA or RNA: store genetic information for virus AK

6. Characteristics of a virus
Same as living cells
Different from living cells
Changes over time
Contain genetic info
Reproduction only inside host
Does not grow
No energy needed needed AK

7. What does a virus need to reproduce?
Grow and reproduce by infecting living cells
Nutrients and cellular machinery of their hosts OJ

8. What types of cells do viruses infect?
Plant viruses -> plant cells
Animal viruses -> animal cells
Bacteriophages -> virus that infects bacteria
     OJ

9. The common cold Virus enters -> invades -> replicates Virus
Mistaken identity of viral RNA
Host assembles virus particles -> infects cells
All within 8 hours
Virus OJ

10. HIV Group of RNA -> Retroviruses Contains RNA as its genetic info
RNA -> DNA not DNA -> RNA
Replication of RNA -> DNA  copy of viral RNA is made
Remains dormant -> once activated (can be many years) 
Before destruction of the immune system OJ

11. Lytic Infections Virus enters a bacterial cell Makes copies of itself
Causes the cell to burst WG

12. Lytic Cycle Virus injects its DNA into host cell
Cell uses virus' information
Makes mRNA from viral info.
Viral mRNA makes viral protein
Viral protein chops up host cell's DNA WG

13. Lysogenic Cycle Prophage: bacteriophage embedded in host DNA
Virus injects DNA into bacterium
Viral DNA in bacterial chromosome WG

14. Lysogenic CYcle (continued)
Prophage replicates w/ bacterium for generations
Prophage exits chromosome
Enters Lytic Cycle WG

15. Lytic vs. Lysogenic Cycle
Lytic Cycle
Lysogenic Cycle
Virus injects DNA into bacterium
Protein synthesis with viral info.
Viral nucleic acids       new viruses
Viral enzymes lyse the cell wall
Viruses escape       infect new cells
Virus injects DNA into bacterium
Viral DNA      bacterial chromosome
Viral DNA is now called a prophage
Prophage replicates with bacterium for generatons
Prophage exits bacterial chromosome (enters Lytic Cycle) WG

16. How can you tell that a virus is not living?
They do not breath
A virus uses sunlight for energy
Viruses crystalize
They are made of proteins C Ak

17. What makes Virus Cells different from Living cells?
The cell does not need energy
Energy is needed for reproduction
Reproduction occurs outside the host
Does not contain genetic information A AK

18. HOW IS THE GENETIC INFORMATION OF A RETROVIRUS COPIED?
A.) DNA -> RNA B.) RNA -> DNA C.) Complementary DNA -> DNA D.) No replication B OJ

19. A.) 9 hours B.) 6 hours C.) 8 hours D.) One day
How many hours does it take for the host cell to release the virus particles and to infect other cells? C OJ

20. WHAT INFECTION CAUSES THE CELL TO BURST?
A.) Prophage Infection B.) Lytic Infection C.) Capsid Infection D.) Lysogenic Infection B WG

21. WHat infection takes generations to set in?
A.) Lysogenic Infection B.) Lytic Infection C.) Viral Infection D.) Bacteriophagal Infection A WG

22. Overview What is a virus? Characteristics of a virus
Viral Reproduction 
RNA Viruses
Lytic infections
Lytic Cycle vs. Lysogenic Cycle