Viruses, viroids, and prions For Dr. Wright’s Bio 27 Class SI Biology SI Session Viruses, viroids, and prions Fall 2009 For Dr. Wright’s Bio 27 Class Picture from http://individ.blogspot.com/ http://micro.magnet.fsu.edu/cells/virus.htm Designed by Pyeongsug Kim ©2009 sibio@att.net

Supplemental instruction For Dr. Wright’s Bio 7/27 Class Virus, Viroid, Prion Supplemental instruction Fall 2010 For Dr. Wright’s Bio 7/27 Class Picture from: http://www.wiley.com/college/boyer/0470003790/cutting_edge/prions/prion1.gif Designed by Pyeongsug Kim ©2010 sibio@att.net

Questions on viruses, viroids, and prions << Part I>> What do we mean when we say a virus is lytic? Temperate? Can a cell shed virus but not itself be killed? What two structures do all viruses have in common? Why do we say that a virus is not alive (i.e., what does it lack?) What do we mean when we say a virus is enveloped? How does such a virus get out of the host cell? What do we mean when we say a virus is naked? Why would a temperate phage cause a lysogenic infection? What type of stimulus would cause it to become lytic again? Give two examples of lysogenic conversion? What is transduction? What is a viroid made of? What types of organisms does it infect? How can viroid infection be controlled? What is a prion made of? What types of organisms (and tissues within) does it infect? How can prion infection be controlled? << Part II>> (Not Yet) .. What implications does this have for control of viral activity? Are all virus genomes the same? What are some types of genomes seen in viruses but not cellular organisms? How does a latent infection alter the genome of the host cell? What are the stages of viral infection? What is the cytopathic effect? Why can measuring antibody levels indicate that an individual has been infected by a particular virus? Compare and contrast acute, late, chronic and latent infections? Give an example of a virus that causes each. In which of these conditions does the person remain a carrier? (i.e., continue to produce infectious virus?) Which of these can persist for a long time? How are such diseases cured? How can a virus cause tumors? What type of gene is mutated to give rise to a tumor? What are two ways that viruses can introduce such mutations? Are most tumors caused this way? In animals, viruses attach to specific receptors on host cells. There are no such receptors in plants. How, then, do viruses infect plants? -Dr. Wright’s Bio 27 Study guide. Fall 2009

Designed by Pyeongsug Kim, ©2009 Viruses -Nonliving -naked or enveloped -have a protein capsid -nucleic acid ~DNA or RNA, but not both -need the host for replication infect every living thing -take over metabolism of the host cell and kill it. -Some virus live in harmony with their hosts. Naked virus Enveloped virus Picture from http://micro.magnet.fsu.edu/cells/virus.htm http://www.csa.com/discoveryguides/avian/images/virus.jpg Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Viroids -Nonliving Smallest particle able to replicate -Naked; without protein coat. -Nuclec acid ______ only -single viroid can infect cell resistant to proteases and nucleases -replicate autonomously -Plant phathogens *as far as we know RNA Picture from http://vegetablemdonline.ppath.cornell.edu/photopages/Potatoes/Viruses/PotVirusFS3.htm http://www.gidabilimi.com/forum/58-genel-mikrobiyoloji/1892-viroidler Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Prions -Nonliving; infectious _______ -No nucleic acid neither DNA or RNA -involved in human and mammalian prion diseases is called “PrP” e.g. mad cow disease -may be removed by __________. proteins autoclaving Picture from http://www.unl.edu/virologycenter/research/research_graphics/bessenbig.gif Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Viruses -infect every living thing -_____________ Viruses that infect bacteria. Bacteriophages(or shortly “phages”) Picture from http://www.geocities.com/madokagm/BIOL1551/lecture_notes_Nov_22.htm Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 cycle -Phage(the virus) injects its DNA makes more phage the cell lysis (the bacteria bursts) Lytic cycle. :be released from a cell, but not kill the cell. -Phage(the virus) injects its DNA -the DNA integrates into the bacaterium's DNA -if the cell copies itself, the virus DNA is also copied with it. -the DNA from the virus stays in the cell. -used commonly as a genetic tool; DNA technology. -Lysogenic conversion may occur. Lysogenic Picture from http://www.geocities.com/madokagm/BIOL1551/lecture_notes_Nov_22.htm Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 phages. -transfer DNA into the host cells -multiplies either as plasmid or integrated into the chromosome of the host. - Harmony with the bacteria. -can either lyse their host or replicate with it. -lambda() Temperate infection - show no sign that cell are infected. - HIV infection Latent Picture from https://eapbiofield.wikispaces.com/Chapter+9+Classification+Janie https://eapbiofield.wikispaces.com/file/view/virus2.gif Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Lambda() - Temperate phage - lysogenizes E. Coli - Some of bacteria will be lysed, other bacteria will be lysogenized. Lytic if bacteria are actively dividing Otherwise lysogenic. - Prophage :integrated into host genome Picture from http://www.waksmanfoundation.org/labs/rochester/bactertiter.htm Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Picture from Dr. Wright’s Bio27 slide Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 ________________ - When a cell becomes lysogenized, phage DNA integrated into the chromosome of the host.  (occasionally) extra genes carried by the phage get expressed in the cell. change the properties of the bacterial cell.(new strains) - e.g. Toxins in C.botulism (Botulism) Lysogenic conversion *After virus infection, “good guy” may become “bad guy” through lysogenic conversion or the other way around. In the lab, lysogenic conversion is used for genetic engineering. Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Temperate, Lysogenic, Lysogenic conversion, Lytic, Lytic _________ Some phases lyse their host cells. _________ Some are extruded w/o killing the host. _________ Most live in harmony with them. _________ The latter often code for gene products that confer new properties on the host. Lysogenic Temperate Lysogenic conversion Picture from http://betterhealthnaturally.files.wordpress.com/2007/10/virus1.jpg Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 _____________ phage-mediated genetic transfer DNA can be transferred from on bacterial cell to another. Transduction Picture from: https://eapbiofield.wikispaces.com/Chapter+27+Guided+Reading+lep?f=print Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Transduction (cont’d) 1) __________ transduction - any bacterial gene can be transferred 2) __________ - virus inserted in a specific site so only genes adjacent to it are transferred (i.e., temperate phages) Generalized Specialized Designed by Pyeongsug Kim, ©2009

Designed by Pyeongsug Kim, ©2009 Genetic transfer from one bacterial cell to another. Conjugation __________ - Sex pili; Virus not involved. Transduction __________ - Generalized; Specialized. Picture from: https://eapbiofield.wikispaces.com/Chapter+27+Guided+Reading+lep?f=print Designed by Pyeongsug Kim, ©2009