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A. Viruses
1. General
a. Defn – Infectious particles that act as obligate parasites – can perform no functions
when outside the host.
b. don’t use binomial nom., often named for disease
2. Structure
a. Protien coat
1) Surround, protects genetic material
2) regular, crystalline appearance
3) small number have membrane around PC (enveloped virus)
b. Genetic material
1) DNA - ~1/3 of viruses,
a) Most double stranded – like Eukaryotes (chick. Pox, Herpes, warts)
b) Some single strand (parvovirus in dogs)
c) more stable, directly compatible w/ host
2) RNA – 2/3 of viruses
a) almost all single stranded (Polio, Flu, measles, AIDS)
b) one type double (infant diarrhea)
c) less stable, not always compatible, mutation
d) reverse polymerization – DNA from RNA
3. Viral reproduction methods
a. Lytic cycle
1) Charge! Strategy – immediate reproduction
2) Mechanism
a) Penetration – entire virus or just gen mat enters host cell.
b) Multiplication – immediate
1)) nucleic acids processing
a)) translation - produce mRNA for protein synth.
b)) replication – duplicate viral RNA
2)) Protein synthesis begins – protein coat
3)) Assembly – Nuc acid/Protein
4)) Release – cells lys, cycle repeats
b. Lysogenic cycle
1) lie in wait - delayed reproduction
2) Mechanism
a) Penetration – same as lytic
b) Multiplication
1)) nucleic acids processing
a)) reverse transcription if RNA
2)) Integration
a)) DNA is incorporated into host DNA
3)) Latency
a)) DNA replicates harmlessly w/ host DNA for period of time
4) Activation – Lytic cycle begins as above