1. Virology Introduction Viral Structure Bacteriophage Replication
Animal Virus Replication
Cancer

2. Virology - Introduction
Viruses are obligate intracellular parasites
Viruses are considered nonliving because they cannot reproduce on their own
Viruses contain DNA or RNA either of which is double or single stranded

3. Virology - Introduction
Host Range
Refers to range of tissue virus can infect
Most viruses can only infect a specific type of tissue within a host
Host range is determined by receptors found on found on tissue cell surfaces

4. Virology - Introduction
Viral Size
Determined by electron microscopy; viruses cannot be seen under light microscope
Viruses range from 20 to nm

5. Virology - Structure

7. Virology - Structure
A viron is a complete fully developed particle composed of nucleic acid and surrounded by a protein coat
Nucleic acid
Capsid and Envelope
General Morphology

8. Virology - Structure Nucleic Acid
Double stranded DNA
Single stranded DNA
Double stranded RNA
Single stranded RNA
Nucleic acid can be 1% to 50% of weight of virus particle

9. Virology - Structure Capsid and Envelope
The protein coat surrounding the nucleic acid is a capsid
Capsid is composed subunits called capsomeres
Capsid of some viruses is enclosed by an envelope consisting of lipids, proteins & carbohydrates
Some envelopes are covered with carbohydrate-protein complexes called spikes

10. Virology - Structure

15. Virology - Phage Replication
Phases
Attachment
Penetration
Biosynthesis
Maturation
Release
Lysogeny

16. Virology - Phage Replication
Attachment - bacteriophage attaches to cell wall
Penetration - phage makes opening in cell and injects DNA
Biosynthesis - phage DNA directs synthesis of viral protein & nucleic acid

17. Virology - Phage Replication
Maturation - Viral components are assembled into virions
Release - Host cell lyses and virions are released into surrounding medium
Lysogeny - Instead of biosynthesis, maturation & release, nucleic acid is integrated into genome becoming a prophage

20. Virology - Replication
Animal Viruses
Attachment - uses receptors on cell surfaces often using “spikes” on virus
Penetration - whole virus enters cell via endocytosis; enveloped viruses can fuse with cell membrane
Uncoating - Virus capsid is removed

21. Virology - Replication
Animal Viruses
Biosynthesis - early & late transcription produce virus enzymes, viral nucleic acid & capsid proteins, respectively
Maturation - virus particles are assembled
Release - Virus particles are exported

23. Virology - Replication
RNA containing viruses
produce reverse transcriptase to make complimentary DNA (cDNA)
DNA then directs synthesis of viral components

26. Virology - Survey Human Viruses
Viruses are grouped by families
Similar DNA sequences & structure

31. Virology - Cancer Cancer causing viruses first identified in chickens
Cancer causing viruses use genes derived originally from host
Cancer causing process is called tranformation

32. Virology - Cancer Cancer causing viruses in humans
Epstein-Barr virus (a herpes like virus) associated with Burkitt’s lymphoma (a relatively rare cancer in children in Africa)
Herpes virus associated with cervical cancer
Human papilloma virus causes genital warts but can also cause cervical cancer (some strains)