1. Headings Vocab Important Info
VIRUSES
Headings
Vocab
Important Info

2. Characteristics of Viruses
Tiny, non-living particles
Do not respire, move or grow
Cannot reproduce on their own
Must reproduce inside of a host cell
Typical infection = 7-10 days
Not given Latin names:
named for disease caused
organ infected
region detected
***Draw Fig page 483

3. Virus Structure All viruses = 2 basic parts:
nucleic acid
protein coat (capsid)
Capsid: protein coat containing inner core of: DNA or RNA
Protein coat gives viruses diff. shapes:
Polyhedral
Cylindrical
round, etc.
May have tail fibers and projections to aid in attachment
Some have extra outer layer called: Envelope

4. Viral Recognition & Attachment
Virus must recognize specific receptor site on host cell
Lands on host and “locks in”
Attachment is specific:
virus can enter and reproduce in only a few types of cells
Ex: Tobacco Mosaic Virus cannot affect human cells even though we are exposed to it daily
                  

5. Viral Reproduction. Viruses must reproduce inside of a host cell
They are classified as Intracellular Parasites
The method of entry into the host cell depends on the virus
There are two main types of viral reproduction:
Lytic cycle
Lysogenic cycle

6. Steps of the Lytic Cycle
ATTACHMENT: Bacteriophage attaches to the cell surface of a bacterium
2. ENTRY: DNA enters bacterial cell

7. 3. REPLICATION: Bacteriophage is replicated & proteins are synthesized
4. ASSEMBLY: “Phage” components are assembled into mature viruses
5. RELEASE/LYSES: Bacterial cell lyses & releases many “phages” that can now infect other cells

9. Lysogenic Cycle Viruses attack cells Do not kill cell immediately
Viral DNA is mixed with host DNA
Does not immediately begin to reproduce
Host cell may function normally while virus stays dormant
Example: Herpes (cold sores, fever blisters)

10. Steps of the Lysogenic Cycle
ATTACHMENT: “Phage” attaches to cell surface of bacterium
PENETRATION: “Phage” DNA enters the bacterial cell
INTEGRATION: “Phage” DNA integrates into bacterial DNA
REPLICATION: Integrated Prophage replicates when bacterial DNA replicates
These cells may show new properties
Steps of the Lysogenic Cycle