1. Viruses

2. Evolution of Virus Alive or Not Biologically inert
Unable to replicate genes
Unable to regenerate ATP
probably evolved as bits of cellular nucleic acid

3. Structural Component of Virus
small infectious particles
nucleic acid
Double or single stranded DNA
Double or single stranded RNA
Single circular molecule or linear
Capsid
Protein shell
some cases, a membranous envelope
Made from membrane of host cell

4. Virus structure

5. Obligate intracellular parasites
Replicate only in host cells

6. Identification of a host cell
Lock and key
Viral surface proteins and specific receptor molecules of the host

7. Bacteriophage Virus that infects bacteria Bacterial Defenses
Natural selection
Restriction enzymes
Lysogeny
Co-exist

8. Lytic vs Lysogenic

9. Retrovirus Equipped with RNA transcriptase RNA DNA
DNA can enter the nucleus into the host genome
HIV

10. Viral Infections in Animals
Damage or kill cells
Produce toxins
Defense tools
Vaccines
Anti-viral drugs

11. Viral infections in Plants
Horizontal transmission
entering through damaged cell walls
Vertical transmission
inheriting the virus from a parent

12. Viroids and Prions Viroids Prions
circular RNA molecules that infect plants and disrupt their growth
Prions
slow-acting
virtually indestructible infectious proteins
brain diseases in mammals – mad cow
propagate by converting normal proteins into the prion version