Viruses

Virus: Particles of nucleic acid, protein, some lipids Reproduce vicariously Use the cells they infect to build new viruses

Viruses: Nucleic Acids: -DNA or RNA -single strand or double strand Capsid: proteins coat that enables infection of cell

Viral Specificity and Adaptation -Infections are highly specific (animal viruses, bacterial viruses, etc.) -Viruses evolve to “jump” species lines -Evolution occurs when the virus takes up DNA from host

Virus Forms

Pathogenicity and Virulence Pathogenicity: The ability of a microbe to cause disease Virulence: degree of pathogenicity -measured by infection rates or fatality

2 forms of Infection 1.Lytic: bursts host cell 2.Lysogenic: doesn’t burst cell

1. Lytic Infection Steps 1.Virus enters host cell 2.Releases DNA/RNA 3.Host transcribes and translates viral nucleic acid 4.Host assembles new viruses 5.New viruses break out of cell and infect new cells

2. Lysogenic Cycle 1.Viral DNA is integrated into host cell’s 2.Replicates the virus DNA with its own 3.Virus remains dormant 4.May enter the lytic cycle

Retroviruses -Contain RNA -Inserts into the DNA of host -Genetic info is copied backwards -Often used in biotech Ex. Gene therapy for Cystic Fibrosis

Gene Therapy