Chapter 17 viruses fall '08 (rev)

Chapter 17 viruses - Chapter 17 17 Viruses& Viroids& Prions Today we will Today Lecture on viruses prions viroids The bulk of today’s

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Unformatted text preview: Chapter 17 17 Viruses & Viroids & Prions Today we will Today Lecture on viruses, prions, viroids The bulk of today’s material is not in the book The not A minute acellular pathogen Not alive Just a “chemical assembly” Therefore must use a host to reproduce as an “obligate intracellular parasite” Cannot reproduce on their own Cannot Use a cell as a replication “factory” Use replication also Cannot independently perform metabolic activities All have capsid nucleic acid ss/ds DNA ss/ds RNA Some, mostly animal viruses, have an “envelope”, usually a phospholipid 1/5 Roles of a virus bad guy: a pathogen = a disease-causing agent “a piece of bad news wrapped in a protein” GOOD GUY Provided most of the evidence that genes are made of DNA Critical in working out how DNA works Began when Began No one knows – No fossil evidence – Undergoes rapid DNA/RNA mutations therefore no genetic trail therefore Began as Began ???? Maybe renegade RNA or DNA Maybe Maybe bits of cell fragments Maybe NOW they think NOW Maybe the precursor to living cells –Have the same kinds of proteins and –DNA/RNA as living cells Minivirus Has its own distinct DNA Up to 5 tRNA ?? separate Domain ?? Alive or not, they are fundamentally important players in evolution constantly mutating produce new genes some useful these genes can be permanently incorporated into the genome of host cell Genetic engineering Discovered Late 19th century Late – Hoof & mouth disease – Isolated virus – Could not replicate Wendell Stanley (1933) – Tobacco mosaic virus Precipitated as crystals – THEREFORE: virus is chemical in nature Not alive Typical Eukaryotic Cell Typical Prokaryotic cell SIZE Really, really small really small Biggest 1000 nanometers Smallest 17 nanometers 8 meters virus Comes in a variety of shapes ????? ??? ??? ?? A RETROVIRUS HOW CLASSIFIED? HOW 3 Types Types Plant Bacteriophage Animal Plant viruses Plant Enters a plant cell Enters via rips, tears, etc. via No cures – FIX: can breed plants FIX: that are genetically resistant to a virus resistant E.g. tobacco mosaic E.g. virus – Tobacco, tomato, Tobacco, squash, cantaloupe squash, Tobacco mosaic virus Bacteriophage Bacteriophage Only invade bacteria Protein sheath DNA in head Bacteriophage Bacteriophage Only invade bacteria Enters by making a hole in Enters cell membrane via enzyme cell action action – Transformation is action Protein sheath DNA in head bacteriophages bacteriophages Bacteriophage Bacteriophage Only invade bacteria Mostly a DNA virus Punch holes in membrane Have 2 life cycles 1.Lytic Uses cell as host to Uses repro repro 2. Lysogenic Lysogenic Hides in host cell Hides DNA until stress, then repros then – BOTH cycles cause BOTH cell death by lysing cell lysing DNA in head Protein sheath 5 steps Bacteriophage Bacteriophage Only invade bacteria Mostly a DNA virus Punch holes in membrane Protein sheath Have 2 life cycles – Lytic Uses cell as host to repro – & lysogenic Hides in host cell until stress, then repros – BOTH cycles cause cell death by lysing lys – Lysogeny is – Transformation is DNA in head ANIMAL VIRUSES ANIMAL Infect animals – Associated with a particular type of cell Nerve – polio Liver – hepatitis Brain – rabies Helper T-cells – AIDS/HIV Human Papillomavirus (HPV) Human 100+ ANIMAL VIRUSES ANIMAL Infect animals – Associated with a particular type of cell Nerve – polio Liver – hepatitis Brain – rabies Helper T-cells -- AIDS CONTROLLED BY IMMUNE SYS Via antibodies and T-cell complex AND VACCINES How viruses destroyed How A review Animal Viruses Animal Life Cycle Life Listen please AIDS AIDS Acquired Immunodeficiency Syndrome Acquired Syndrome A disorder that destroys the body’s ability disorder to protect itself to AIDS AIDS Acquired Immunodeficiency Syndrome A disorder that destroys the body’s ability to protect itself In humans, caused by HIV In = human immunodeficiency virus human AIDS AIDS Acquired Immunodeficiency Syndrome A disorder that destroys the body’s ability to protect itself In humans a cause is HIV = human immunodeficiency virus – Enters body via rips, tears, semen, vaginal Enters lining, blood lining, – It is a retrovirus = uses an enzyme to reverse It retrovirus engineer RNA to DNA engineer Reverse transcriptase Infects and eventually lyses body’s helper T-cells Infects You die because you can no longer fight off infections You How viruses destroyed How A review Animal Viruses Animal Life Cycle Life Listen please AIDS AIDS Acquired Immunodeficiency Syndrome Acquired Syndrome A disorder that destroys the body’s ability disorder to protect itself to AIDS AIDS Acquired Immunodeficiency Syndrome A disorder that destroys the body’s ability to protect itself In humans, caused by HIV In – = human immunodeficiency virus human AIDS AIDS Acquired Immunodeficiency Syndrome A disorder that destroys the body’s ability to protect itself In humans a cause is HIV = human immunodeficiency virus – Enters body via rips, tears, semen, vaginal Enters lining, blood lining, – It is a retrovirus = uses an enzyme to reverse It retrovirus engineer RNA to DNA engineer Infects and eventually lyses body’s helper T-cells Infects Lack of helper T-cells lowers body’s resistance to infections You die because you can no longer fight off infections You AIDS AIDS Acquired Immunodeficiency Syndrome A disorder that destroys the body’s ability to protect itself In humans a cause is HIV = human immunodeficiency virus – Enters body via rips, tears, semen, vaginal lining, blood – Infects and eventually lyses body’s WBCs (helper T-cells) – Lack of helper T-cells lowers body’s resistance to infections Lack – It is a retrovirus = a RNA virus that repros via host cell’s DNA Areas in Africa have a 40+% infection rate – $15 Billion BUT conditions on use of money Can be infected long time e.g. 10 years before Can signs HOW POSSIBLE?????? signs Glycoprotei n “gp 120” ?? ?? ? An enzyme that reverse engineers RNA to DNA The HIV virus A retrovirus HIV works how??? HIV Cd4 Ccr5 Cd4 cxcr4 PE EL H S OY TR S DE LL CE T R MEASLES CHICKEN POX RABIES SMALLPOX SMALLPOX MUMPS COLDS HEPATITIS H virus lll Problems l sma FL U POLIO HERPES HERPES MEASLES CHICKEN POX CONTROLLED BY SMALLPOX SMALLPOX IMMUNE SYS FL Via antibodies aU nd H T-cell complex RABIES MUMPS COLDS HEPATITIS n Problems uma AND VACCINES POLIO HERPES HERPES FLU aka influenza aka 3 types (determined by different capsids) – Type A Type – Type B – Type C BAD BAD (humans birds mammals) (humans <<<<<Mild (only humans) ll have subtypes = different flu strains Caused by different surface proteins • hemagglutinin (cell entry) (13) • neuraminidase (cell wall destroyer) (9) •Named by T?(H?N?) Prions Prions (PRONOUNCED “PREE ON” Stanley Prusiner CJD Proteinaceous infectious particle – No DNA or RNA – A new biological principle of infection PrP protein – Gene mutations yield misfolded protein = Prion Prion Induces other PrP proteins to become pathogenic prions How Done? Prions different strains found differ in conformatiom in properties in diseases they cause TSE transmissible spongiform encephalopathy transmissible or spongy brain disease or PRIONS PRIONS TSE is known as – Scrapie in sheep – Mad cow disease in cattle in Chronic Wasting Disease vCJD vCJD – CJD or Kuru-Creutzfeldt-Jakeb disease in Kuru-Creutzfeldt-Jakeb humans humans Can have 10-45 year incubation period No cure Scrapie in a hamster brain. Note sponge-like appearance Normal densely packed brain cells VIROIDS VIROIDS Another non-living infectious agent Is just a short strand of RNA – 250-450 nucleotides VIROIDS VIROIDS Another non-living infectious agent Uses cellular enzymes to replicate VIROIDS VIROIDS Another non-living infectious agent Is just strand RNA Uses cellular enzymes to replicate Affects only plants Transmitted by seeds or pollen Transmitted – Stunts growth Not known how Not – But found in host cell nucleus – ?disrupt gene regulation (disrupts metabolism? By causing cell’s ribosomes to change structure?) – Killed 10 million coconut trees in Philippines Again we say amen amen ...
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This note was uploaded on 06/02/2011 for the course BIOL 110 taught by Professor Duwel during the Fall '08 term at South Carolina.

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