Chapter 18.2 Viruses and Prions. “Viruses and prions are smaller and less complex than bacteria; they invade cells and can alter cellular functions.”. Chapter 18.2 Learning Targets. Illustrate the general structure of viruses.
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Chapter 18.2 Viruses and Prions “Viruses and prions are smaller and less complex than bacteria;they invade cells and can alter cellular functions.”
Chapter 18.2 Learning Targets • Illustrate the general structure of viruses. • Compare and contrast the sequence of events in viral replication by the lytic cycle, the lyosgenic cycle, and retroviral replication. • Discuss the structure, replication, and action of prions in relationship to causing disease.
Characteristics T-4 Virus - infects E. coli • non-living particles • invade living cells • pathogenic - named after the disease they cause or organ they infect • smallest of all organisms
VIRUS - an obligate intracellular parasite INFECTIOUS MONONUCLEOSIS
Origin of Viruses Wendell Stanley (1904 - 1971) first isolated TMV in 1935. • Viruses may have originated from host cells • 1935 - first seen by an electron microscope • Tobacco mosaic virus - first virus discovered - 1886
1886 - “Living Fluid Infectant” - the virus passed through filters that held bacteria.
Viral Structure • Inner core - contains viral DNA or RNA (never both) • Capsid - outer coat of protein • Envelope - outer layer on larger viruses
Viral ReplicationLytic Cycle • 1. Attachment • 2. Injection • 3. Replication • 4. Assembly • 5. Lysis
LYSOGENIC CYCLE 1. Attachment 2. Injection • Viral DNA integration (provirus) 4. Cell division 5. Replication 6. Assembly 7. Lysis
L Y S O G E N I C L Y T I C
VirusesBozeman Biology http://www.youtube.com/watch?v=L8oHs7G_syI 8:06 min.
VIRUSESCHAPTER 18 Part 2
SmallpoxVariola (Major & Minor) • First virus to be studied in detail • Edward Jenner - 1798 • First vaccine - cowpox virus (vaccinia virus)
(Ali Maow of Merka, Somalia, contracted smallpox in 1977 at the age of 23. His was the last known case of smallpox in the world.) Last case of smallpox
Icosahedral Virus(many sides) Wart virus Polio - Naked, small, icosahedral virus
Enveloped Virus INFLUENZA VIRUS
E-Coli Bacteria BACTERIOPHAGE
HIV Retroviruses • RNA viruses • Reverse transcriptase - makes DNA from its RNA • Includes HIV, polio & some cancers
The Immune SystemBozeman Biology http://www.youtube.com/watch?v=L8oHs7G_syI 13:47 min.
When HIV Becomes AIDS (HIV #2) http://www.youtube.com/watch?v=68I7JlVhuhY 3:56 min
PATHWAY OF RABIES VIRUS