VIRUSES
Characteristics of Viruses
• Tiny, ______particles
• Do ______respire, move or grow
• ______
– Must reproduce inside of a host cell
• Typical infection = 7-10 days
• ______given Latin names:
– named for disease caused
– organ infected
– region detected
Virus Structure
• All viruses = 2 basic parts:
– ______
– ______(capsid)
• ______: protein coat containing inner core of:______or ______
• Protein coat gives viruses diff. shapes:
– Polyhedral
– Cylindrical
– round, etc.
• May have tail fibers and projections to aid in ______
• Some have extra outer layer called: ______
Viral Recognition & Attachment
• Virus must recognize ______on host cell
• Lands on host and “______”
• Attachment is specific:
– Virus can enter and reproduce in only a few types of cells
• Ex: ______cannot affect human cells even though we are exposed to it daily
Viral Reproduction
• Viruses must reproduce ______of a ______
• They are classified as ______
• The method of entry into the host cell depends on virus
• There are two main types of Viral Reproduction:
– ______
– ______
Steps of the Lytic Cycle
1.______: Bacteriophage attaches to the cell surface of a bacterium
2. ______: DNA enters bacterial cell
3.______: Bacteriophage is replicated & proteins are synthesized
4.______: “Phage” components are assembled into mature viruses
5.______: Bacterial cell lyses & releases many “phages” that can now infect other cells
Lysogenic Cycle
• Viruses attack cells
– Do ______kill cell immediately
• Viral DNA is ______with host DNA
• Does not immediately begin to reproduce
– Host may function ______while virus stays ______
• Example: ______(cold sores, fever blisters)
Steps of the Lysogenic Cycle
1.______: “Phage” attaches to cell surface of bacterium
2.______: “Phage” DNA enters the bacterial cell
3.______: “Phage” DNA integrates into bacterial DNA
4.______: Integrated ______replicates when bacterial DNA replicates
1.These cells may show new properties
***IN 148: Draw Figure 19-3
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