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Viruses

Viruses

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Viruses

A. Characteristics

B. Structure and Function

C. Classification

D. Diseases

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A. Characteristics

1. A virusis an infectiousparticle that can causedisease

2. Smaller than a cell (25-250nanometers)

a. Shadow Casting

3. Needs host cell toreproduce

4. Not alive Origin?

a. Degenerate Evolution

b. Escaped Nucleic Acidsc. Extraterrestrial_Click

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B. Structure and Function

1. Composed of DNA or RNAsurrounded by a protein coatcalled a capsid

2. Some aresurrounded by amembrane (envelope)

3. Many shapes: helical, head andtail, oricosahedral_

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4. Reproduceonly in living cellsby lytic and lysogenic lifecycles

a. lytic cycle takesover andkillsrapidly

b. lysogenic cyclewaitsinthe cell until theorganism isweak, thenenters the lytic cycle

(Transduction bytemperate phage)

Prophage DNA insertedinto bacteria host genome

Provirus DNA inserted intoa human chromosome_

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5. HIVis a retrovirus thatcauses AIDS

a. able toevolverapidly_

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C. Classification

1. DNA Viruses inject DNAinto host (2 options)

a. DNA codesfor new RNA

b. DNA fuseswith host DNA

2. RNA Virusesa. Direct protein synthesis

b. Retrovirus usesreversetranscriptase to makenew DNA (HIV)_

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3. Viroids

a. Smallest replicatingparticles

b. Short, singlestrand ofnaked RNA

c. Causes diseasein plants

4. Prions

a. Disease causingglycoprotein particlecontaining approx. 250amino acids

b. No nucleic acids

c. (Ex. Kuru, Scrapie, MadCow Disease)_

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D. Diseases

1. Each infects a certain host orhosts and cause diseasein:

a. animals and plants

b. fungus and protists

c. even bacteria(bacteriophage)_

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2. Spread by insects, air, water,and people

3. Controlled by:

a. Antibodies- help destroyviruses by attaching to

them

b. Vaccines-

1. Inactivated Cantreplicate

2. Attenuated Genetically altered tonot cause disease (bestand longest protection)_

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c. Interferon- interfereswith doublestrandedRNA

d. Antiviral drugs

1. Acyclovir Herpes

and Chickenpox(mimics nucleosides)

2. AZT AIDS

3. Protease Inhibitors

e. Eradication - Smallpox_

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E. Examples (Shapes)

1. Polyhedral

Warts

Polio

Hepatitis

Colds

Conjunctivitis

Sore throat

Respiratory

Intestinal_

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2. Enveloped Polyhedral

Herpes

Chicken Pox

Shingles

Mono_

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3. Helical

Smallpox Last Case1977

Tobacco Mosaic

(Crystallized in 1935 by

Wend

ell Stanl

ey F

irst t

odetermine that viruses are

not madeof cells)_

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4. Enveloped Helical

Flu A, B, C

Rabies_

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5. Glycoprotein EnvelopedComplex

AIDS (uncoating)_

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F. Examples (DNA/RNA)

1. DNA Viruses

Papoviruses Warts, Cancer

Adenoviruses Resp/Intest

Herpesviruses herpessi

mplex, ch

ick

enp

ox,shingles, mono

Poxviruses smallpox,cowpox_

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2. RNA Viruses

Picornaviruses Polio,Hepatitis A, Cancer

Myxoviruses Influenza A,B, C; HepatitisB, C

Rhabdoviruses - Rabies

Retroviruses - AIDS,Cancer_

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G. Future

1. Emerging Viruses Virusesthat jump species when weinvade new habitats

(ex. Ebola, Aids, SARS)

2. Viruses and Cancer

a. HTLV Leukemia

b. HepatitisB Liver Cancer

c. Epstein-Barr BurkittsLymphoma

d. HPV Cervical Cancer_

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3. Mimivirus

CHARACTERISTICS

a. Genomeof1.2 millionletters (10x a typical virus)

b.1

000+ genes

(1

00x typicalvirus)including genesfor

translation and DNA repairenzymes

c. Both DNA and RNA_

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IMPLICATIONS

a. Mimi-like ancestor may

haveemerged prior tootherdomains (New domain may becalled for)

b. Mimi-likes may haveevolved into cells

c. Mimi-likes may havebecome nucleus (Bothreplicateusing cellmachinery, both haveenzymesfor capping RNA,both have linear DNA

d. We may haveevolvedfrom viruses

e. Blurs distinction betweenlife/non-life (Human genomecontains moreretrovirusDNA than actual genes)_

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THEEND

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Viruses

A. Characteristics

B. Structure and Function

C. Diseases

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A. Characteristics

1. A virusis an infectiousparticle that can causedisease

2. Smaller than a cell and canonly beseen with an electronmicroscope

3. Acts as a parasitewhichlives on and getsfood froma host organism

4. Not alive_

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C. Classification

3. Viroids

a. Smallest replicatingparticles

b. Short, singlestrand ofnaked RNA

c. Causes diseasein plants

4. Prions

a. Disease causingglycoprotein particlecontaining approx. 250amino acids

b. No nucleic acids

c. (Ex. Kuru, Scrapie, MadCow Disease)_

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4. Reproduceonly in living cellsby lytic and lysogenic lifecycles

a. lytic cycle takesover andkillsrapidly

b. lysogenic cyclewaitsinthe cell until theorganism isweak, thenenters the lytic cycle_