viruses

1. Viruses

3. Naming of Viruses Disease they cause Rabies virus Polio virus

4. Organ or tissue they infect Adenovirus Attacks adenoid tissue at the back of the throat

5. Bacteriophage A virus that infects bacteria

6. Structure Inner core Contains DNA or RNA (never both) Nucleic acid contains genes that codes only for making DNA copies and nothing else Capsid The protein shell that encloses the nuclei acid Envelope Found in large viruses

8. Shapes of Viruses Depends on the arrangement of the proteins on capsid (viral coat) Plays a role in the infection process

9. Polyhedral Looks like small crystal Most have 20 sides Polio virus and T4 bacteriophage Cylindrical Tobacco mosaic viruses Enveloped viruses Envelope studded with projections HIV and influenza virus

10. Polyhedral

11. Cylindrical

12. Enveloped viruses

13. How do we get infected? Viruses have different proteins on the surface Proteins interact with specific receptor cells on their host�s plasma membrane Attachment of virus to host cell is specific Most can only enter and reproduce in a few kind of cells Some viruses are cell-specific Polio viruses can only infect nerve cells in humans

15. Lytic Cycle DNA injected into cell Transcription/translation of 100 viral genes DNase chops up host DNA DNA modification protects viral DNA Virus undergoes self-assembly Lysozyme chews hole in cell wall ? host cell burst

16. Lytic cycle

17. Lysogenic cycle Viral nucleic acid is inserted into genetic material of host Forms provirus Provirus � virus formed when viral DNA is inserted into the host cell chromosome Host replicates with it Can go undetected in this cycle for years Eventually enter the lytic cycle and kills the host cell

18. Lysogenic cycle

19. Lysogenic viruses

20. Retroviruses HIV RNA as nucleic acid Injects nuclei acid and reverse transcriptase Reverse transcriptase - enzyme that copies viral RNA into DNA Reverse transcriptase is a common name for an enzyme that functions as an RNA-dependent DNA polymerase. They are encoded by retroviruses, where they copy the viral RNA genome into DNA prior to its integration into host cells Reverse transcriptase is a common name for an enzyme that functions as an RNA-dependent DNA polymerase. They are encoded by retroviruses, where they copy the viral RNA genome into DNA prior to its integration into host cells

21. RNA lytic viruses Nucleic acid is RNA but not reverse transcriptase Can only copy RNA to DNA in absence of RT Follow the lytic cycle

22. Plant viruses Tobacco mosaic virus First virus identified May cause distinct coloration or variegation in flowers Not always fatal of harmful Attacks tomato plants