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Chapter 27

Chapter 27. Viruses Joe Ganoe Jesus Trochez. Types of Viruses. Plant Virus Helical capsid shape Animal Virus Icosahedral capsid Bacterial Virus Icosahedral head : helical tail Animal Virus Helical capsid within envelope. Lytic Cycle. Reproductive virus cycle 5 step process

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Chapter 27

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  1. Chapter 27 Viruses Joe Ganoe Jesus Trochez

  2. Types of Viruses • Plant Virus • Helical capsid shape • Animal Virus • Icosahedral capsid • Bacterial Virus • Icosahedral head : helical tail • Animal Virus • Helical capsid within envelope

  3. Lytic Cycle • Reproductive virus cycle • 5 step process • Attachment • Penetration • Synthesis • Assembly • Release

  4. Lytic Cycle Steps • Attachment • Virus attaches to cell wall • Penetration • Viral DNA injected into cell • Synthesis • Protein and nucleic acid form • Assembly • Involves spontaneous assembly of capsid and enzyme to insert DNA • Release • Lysis (disintegration of cell by rupture of its plasma membrane) of cell

  5. Lysogenic Cycle • 3 Step process • Intergration • Propagation • Induction • Starts at the 2nd cycle of the Lytic Cycle (Penetration) • After it ends the virus returns to Synthesis in the Lytic Cycle • This cycle does not immediately kill the cells they infect, but use the cell to make it into another virus cell

  6. Lysogenic cycle • Integration • Integration of genome leads to prophage • Propagation • Propagation of prophage along with host genome • Induction • Induction prophage exits the bacterial chromosome, viral genes are expressed

  7. Key Terms • Lytic cycle • A viral cycle in which the host cell is killed (lyse) by the virus after viral duplication to release viral particles • Lysogenic Cycle • A viral cycle in which the viral DNA becomes integrated into the host chromosome and it replicated during cell reproduction. Results in vertical rather than horizontal transmission • Bacteriophage • A virus that infects bacterial cells • Also called a phage • Capsid • The outermost protein covering a virus • Tissue Tropism • The affinity of a virus fro certain cells with a multicellular host • For example, hepatitis B virus targets liver cells. • Host range • that can be infected by a particular virus • Icosahedron • A structure consisting of 20 equilateral triangular facets • This is commonly seen in viruses and forms one kind of viral capsid • Phage conversion • The range of organismsthe phenomenon by which DNA forma virus, incorporated into a host cell’s genome, alters the host cell’s function in a significant way • Envelope • A casing that protects the virus from being attacked. Only found in animal cells.

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