Download Viruses - Elgin Local Schools

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
Bacterial Plasmids