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 cell2. Lysogenic: doesn’t

burst cell

1. Lytic Infection Steps

1. Virus enters host cell2. Releases DNA/RNA3. 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 dormant4. May enter the lytic

cycle

Retroviruses

- Contain RNA- Inserts into the DNA of

host- Genetic info is copied

backwards- Often used in biotechEx. Gene therapy for

Cystic Fibrosis

Gene Therapy