Virus and Prion Notes

1. Virus and Prion Notes Ch. 18

2. Bacteria and Viruses Chapter 18 18.2 Viruses and Prions Viruses • A nonliving strand of genetic material within a protein coat • No organelles to take in nutrients or use energy • Cannot make proteins • Cannot replicate on their own

3. Viruses – tiny non-cellular particles of genetic material and protein. Controversy over whether living or non-living. Table: Reasons for classifying non-living vs. living

4. Figure 19-11 Viruses and Cells Section 19-2

5. Invasion Methods • Flu Attack! How A Virus Invades Your Body : NPR

6. Bacteriophage Invasion • Bacteriophage invades a bacterium

7. Structure • Contain a nucleic acid and protein • HEAD region • Capsid--protein coat with nucleic acid core • TAIL region • to attach to host

8. Bacteria and Viruses Chapter 18 18.2 Viruses and Prions Viral Infection • In order to replicate, a virus must enter a host cell. • The virus attaches to the host cell using specific receptor site on the plasma membrane. • 3D shape of the virus coat interlocks with the matching site on the host cell (lock and key) • Many viruses cannot be transmitted between different species.

9. Named for: • Disease they cause • Organs they infect • Code Numbers differentiating organs they infect • Bacteriophage – means “bacteria eater” - viruses which attack bacteria

10. RNA DNA Head RNA Capsid Capsid proteins Tail sheath Tail fiber Surface proteins Membrane envelope Figure 19-9 Virus Structures Section 19-2 Tobacco Mosaic Virus T4 Bacteriophage Influenza Virus

12. Bacteria and Viruses Chapter 18 Viral Replication in Prokaryotes occurs in cytoplasm as DNA is not in a nucleus – pgs. 528 – 529 Lytic Cycle • The host cell makes many copies of the viral RNA or DNA. • Lysis of host cell Lysogenic Cycle • Viral DNA inserts, or integrates into a chromosome in a host cell. • Infected cell will have the viral genes permanently. • Viral DNA can separate and enter lytic cycle

13. Animated Lytic Cycle

14. Animated Lysogenic Cycle

15. Bacteria and Viruses Chapter 18 18.2 Viruses and Prions Bacteriophage • A virus that infects bacteria Other Viruses • HIV/AIDS- spread through sexual contact • Rabies- effects nervous system • HPV- cancer causing virus

16. Figure 19-10 Lytic and Lysogenic Infections

17. Bacteria and Viruses Chapter 18 18.2 Viruses and Prions

18. Hepatitis – DNA Virus

19. Herpes Virus – DNA Virus

20. Rhinovirus – RNA virus

21. Polio Virus – RNA Virus

22. SARS Virus – RNA Virus

23. Viral Replication in Eukaryotes occurs in nucleus of cell (not pictured in text) • 1. DNA viral diseases (not listed in text as such) –examples: hepatitis, chicken pox, herpes, shingles • Structure: DNA inside protein coat virus • Reproduction – information follows normal pathway: DNA to RNA to proteins in cell

26. 2. RNA viral diseases p. 526 – cold, mumps, measles, polio, flu, AIDS, SARS, West Nile, most plant viruses a. Structure – RNA wrapped in protein coat, surrounded by an envelope of glycoprotein spikes that bind with the membrane receptor proteins on the host cell b. Reproduction 1. protein surrounding RNA dissolves 2. RNA synthesis occurs – strand produces either new viral RNA or protein for the viral coat and spikes 3. New virus assembles – uses the cell membrane to make an envelope

28. Damage from virus – depends upon • Are cells lysed? (remember what lysis is?) • What type of cell is damaged – polio damages nerves which cannot regenerate Plant Viruses – most are RNA viruses • virus must breach cuticle and cell wall so damaged plants are more susceptible • typically rod shaped • spreads through cytoplasmic connections between plant cell walls • insects and gardening tools can spread to other plants

29. Emerging Viruses – how do they come into being? • Current Hypothesis for Development of First Viruses– first viruses were fragments of cellular nucleic acid that could transfer to another cell. Protein coat later developed for protection/recognition. Viral genetic material is similar to cellular genetic material. • Contributing Factors for current new virus development – • RNA viruses – high mutation rate – RNA replication isn’t proofread so more mistakes. Mutated forms do not trigger previous immunity • Existing viruses may spread to new host – through mutation or new opportunity to infect a new host – Ex: Hanta Virus – to humans from the bites, urine or droppings of infected mice or rats • Existing virus in small populated area becomes widespread as new methods of transmission occur – Ex: HIV

30. Retrovirus – has two copies of RNA instead of one and contains the enzyme reverse transcriptase – Ex: HIV pg. 530 • Reverse transcriptase synthesizes DNA from RNA. Complementary DNA strands are formed • The double strand of DNA is then inserted into host DNA to form a provirus which is the animal version of a prophage • Lysogenic-type cycle runs • Occasionally provirus is transcribed into RNA, makes new viruses which infects other cells

31. RetrovirusThe HIV virus

32. HIV – Retrovirus Life Cycle • Life Cycle of HIV, a Retrovirus

33. Prions – proteinaceous infectious particle (protein that can cause a disease) 1. Normally exist in cells – not sure of function 2. Shape – multi-folded piece of paper 3. Diseases – these diseases belong to a group of diseases called TSEs or transmissible spongiform encephalopathy – prions able to trigger abnormal folding of certain normal cellular proteins called prion proteins that are found in abundance in the brain a. Mad Cow Disease b. variant CJD – variant Creutzfeldt-Jacob disease in humans c. Scrapie in sheep – affects their central nervous system, usually fatal d. chronic wasting disease in deer and elk

34. PrionsProtein particles

35. 4. Prion Infection – a. Causes normal proteins to mutate - in brain cells, causes lysis of cells b. Spread when prions move to new material – not sure how this happens but may occur when: 1. Prion exists in brain or spinal cord of a cow. 2. When the cow is butchered, contamination of the beef occurs from nervous tissue. 3. Humans eat the contaminated beef 4. The prion enters the human’s nervous system.