1. Virus 2. Capsid 3. Envelope

Transcription

1 VIRUSES BIOLOGY II

2 VOCABULARY- VIRUSES (22 Words) 1. Virus 2. Capsid 3. Envelope 4. Provirus 5. Retrovirus 6. Reverse transcriptase 7. Bacteriophage 8. Lytic Cycle 9. Virulent 10. Lysis 11. Lysogenic Cycle 12. Temperate Virus 13. Prophage 14. Vector 15. Protease inhibitor 16. Oncogene 17. Proto-oncogene 18. Emerging Disease 19. Inactivated Virus 20. Attenuated Virus 21. Viroid 22. Prion

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4 A. Viral Structure and Replication 1. Discovery of Viruses a. Virus: a nonliving particle made up of nucleic acid and protein coat or nucleic acid and a lipid-protein coat b. Cause disease and used for genetic research c. Smaller than bacteria 2. Characteristics of Viruses a. Not alive because they lack some key characteristics of living organisms (ex. They don t grow or carry out metabolism) b. They can t reproduce outside a host cell- must use the host cell s ribosomes and other molecules

5 3. Viral Size and Structure a. Smallest particles able to cause disease b. Capsid: a protein sheath that surrounds the nucleic acid core in a virus c. Envelope: a membrane-like layer that covers the capsids of some viruses (ex. HIV, chickenpox, and polio)

6 4. Classification of Viruses a. Viruses are classified by whether they have RNA or DNA, single or double strand, linear or circular, nature of the capsid, and presence or absence of an envelope.

7 5. Viral Replication a. Outside the host cell, a virus is lifeless particle with no control over its movement b. Viruses infect eukaryotes and prokaryotes c. Viral infection start when the virus enters the host and takes over the metabolic machinery of the cell, making new viruses d. Provirus: viral DNA that has attached to a host cell s chromosome and that is replicated with the chromosome s DNA 1. This happens with DNA viruses e. With RNA viruses, it serves directly as mrna, which is made into new viral proteins after infection f. Retroviruses: a virus that contains a single stranded RNA and produces a reverse transcriptase, which converts RNA to DNA (ex. HIV)

8 g. Reverse transcriptase: an enzyme that catalyzes the formation of DNA from an RNA template h. Bacteriophages: viruses that attack bacteria 1. Has helped scientist understand viral replication

9 6. Lytic Cycle a. Lytic Cycle: a method of viral replication that results in the destruction of a host cell and the release of many new virus particles b. Virulent: viruses that reproduce only by the lytic cycle

10 7. Lysogenic Cycle a. Lysogenic: a method of viral replication in which a viral genome is replicated as a provirus without destroying the host cell b. Temperate virus: a virus whose replication includes the lysogenic cycle c. Prophage: the viral genome (DNA) of a bacteriophage that has entered a bacterial cell, has become attached to the bacterial chromosome, and is replicated with host bacterium s DNA

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12 8. The origin of Viruses a. Viruses thought to have evolved from early cells b. First viruses were naked pieces of nucleic acids that entered cells through damaged areas c. Viruses used as a vehicle to replace faulty DNA (ex. Cystic fibrosis) d. Bacteriophages have been invaluable tools for medical research

13 B. Viral Diseases 1. Vectors of Viral Disease a. Vector: an intermediate host that transfers a pathogen or a parasite to another organism b. Ex. Humans, animals, mosquitoes, ticks, and fleas

14 2. Human Viral Disease a. Chickenpox and Shingles 1. multiplies in the lungs and travels via blood to the skin 2. virus, in some cases, can stay in nerve cells as a provirus and later cause shingles 3. spread through direct contact

15 b. Viral Hepatitis 1. Inflammation of the liver caused by at least 5 viruses 2. Hepatitis A and E spread by fecally contaminated food and water- Hepatitis B, C, D are spread by sexual contact 3. Symptoms: fever, nausea, jaundice, and liver failure

16 c. Acquired Immune Deficiency Syndrome (AIDS) 1. Caused by the human immunodeficiency virus (HIV) 2. Destroys a person s immune system- T cells 3. Spread by sexual contact 4. Drug therapies to combat HIV have worked, but due to the viruses ability to evolve, medicines must be switched back and forth to control virus 5. Can t cure disease, must control it

17 d. Viruses and Cancer 1. Cancer results when cells divide at an uncontrolled rate 2. Oncogenes: genes that cause cancer by blocking normal controls of cell reproduction 3. Proto-oncogenes: DNA inserts itself into host s chromosome which controls cell growth 4. Ex. Human papillomavirus, Epstein-Barr virus, and hepatitis B

18 3. Emerging Viral Diseases a. Emerging diseases: illnesses caused by new or reappearing infectious agents that exist in animal b. ex. Ebola, Hantavirus, and SARS

19 4. Prevention and Treatment a. Vaccination 1. a solution that contains a harmless version of a virus, bacterium, or toxin that causes an immune response when introduced to the body 2. inactivated virus: not able to replicate in a host 3. attenuated virus: weakened form of the virus that cannot cause disease b. Vector control c. Drug Therapy- small number of drugs

20 5. Viroids and Prions a. Viroids: smallest known particles that are able to replicate b. Viroids are single strands of RNA with no capsid- infect plants (ex. Coconuts, potatoes, and oranges) c. Prions: infectious protein particles that do not have a genome (ex. Mad cow disease)

21 VIRUS TEST- BIOLOGY II *80 Possible Points *Friday, May 11 th *Part I. Multiple Choice. *Part II. Short Answers points each -Directly from the notes- read through notes! -10 points each -complete sentences 1. Shingles is a disease caused by the same herpesvirus that causes chickenpox. How do you account for the fact that shingles often appears years after the initial chickenpox attack? 2. For viral diseases without known cures, such as AIDS, certain types of hepatitis, and Ebola, identify ways in which the incidence of such disease can be reduced.