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Characterizing and Classifying Viruses, Viroids, and Prions. Chapter 13. Comparing the size of a virus, a bacterium, and a eukaryotic cell. General Features of Viruses #1. Obligate Intracellular Parasites Very small (ultramicroscopic) Non-cellular Not Alive Protein Coat …Capsid
General Features of Viruses #1 • Obligate Intracellular Parasites • Very small (ultramicroscopic) • Non-cellular • Not Alive • Protein Coat …Capsid • Envelopes (some viruses..not all)
General Features of Viruses #2 • Utilization of Host Cell Machinery • Host Range • Genome • DNA or RNA but NOT both • Single stranded or double stranded • Enzymes (Polymerases) (some viruses…not all)
Emerging viral diseases Play Movie
Virus Replication (Video clip-part1)(5 Basic Steps for all viruses) • Adsorption • Penetration • Replication • Maturation • Release
The lysogenic and lytic reproductive cycles of phage , a temperate phage
Lysogenic cycle video clip-part 2 • Lysogeny • Prophage • Temperate virus • Lysogenic conversion • Corynebacterium diptheriae
The reproductive cycle of an enveloped virus • Attachment (adsorption) • Entry and Uncoating • Viral replication and protein synthesis • Assembly (maturation) • Release
Entry and Uncoating of Animal Viruses Figure 13.12a-b
Entry and Uncoatingof Animal Viruses Figure 13.12c
Release of Enveloped Viruses by Budding Figure 13.13
HIV reproduction Play movie
Cancer Some viruses are oncogenic • Protooncogenes • Oncogenes
All forms of life have viruses that infect them Plant viruses
Viroids • Short pieces of “naked” RNA • No Protein coat • Only known to infect plants • Cadang Cadang disease
Prions • Infectious proteins • No nucleic acid involved • Cause degenerative brain diseases • Scrapie in sheep • Mad Cow Disease • Creutzfeldt-Jakob Disease • CWD Chronic Wasting Disease in deer/elk
Chronic Wasting Disease • Chronic Wasting Disease (CWD) is a transmissible neurological disease of deer and elk producing lesions in brains of infected animals. It is characterized by loss of body condition, behavioral abnormalities and death. CWD is classified as a transmissible spongiform encephalopathy (TSE), and is similar to mad cow disease and scrapie.
Prion: CWD • Chronic Wasting Disease Chronic Wasting Disease Among Free-Ranging Cervids by County,United States, January 2007
CWD in Iowa???...Not Yet! • Each season about 4,000 deer are tested…none positive • Since 2002 over 20,000 deer tested without a positive