Virus | CEE Academy

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HISTORY

Table 1: Virus: Important Discoveries

Event / Term	Scientist
Term 'Virus'	Louis Pasteur
Discovery of virus	Ivanowski
Contagium vivum fluidum	Beijerinck
Crystallization of virus	Stanley
Retrovirus + reverse transcriptase	Temin + Baltimore

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MAIN CHARACTERS

Table 1: Living vs Non-living Characters

Character	Feature
Non-living	Can be crystallized
Living	Contains nucleic acid + capable of protein synthesis

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MORPHOLOGY

▢ Size:

Table 1: Virus Size

Type	Virus
Smallest virus	Foot and mouth disease virus
Largest virus	Smallpox virus / Variola virus

▢ Shape:

Table 1: Virus Shape

Shape	Example
Brick-shaped	Smallpox virus
Spherical	Influenza virus
Rod-shaped	TMV
Tadpole-like	Bacteriophages

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NUCLEIC ACID

Table 1: Viral Nucleic Acid Types

Type	Examples
dsDNA	• Herpes simplex virus • Hepatitis-B virus • Adenovirus Pox virus: • Smallpox / Variola • Chickenpox / Varicella-zoster • Epstein-Barr virus Some plant viruses: • Cauliflower mosaic virus • Dahlia mosaic virus
ssDNA	• Bacteriophage \(\phi X174\)
dsRNA	• Wound tumour virus • Rice dwarf virus • Reovirus
ssRNA	• All hepatitis viruses except Hepatitis-B virus • Polio virus • Influenza virus • AIDS virus • Measles virus • Mumps virus • Rabies virus • Tobacco mosaic virus • Rous sarcoma virus • Rhinovirus / common cold virus • Yellow fever virus • Dengue fever virus

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TERMS

▢ Prion / Slow Virus:

❖ Definition: Proteinaceous infectious agent

❖ Key Point: Smallest pathological agent causing disease

❖ Diseases:

Table 1: Prion Diseases

Disease	Key Point
Mad cow disease / Creutzfeldt-Jakob disease	Fatal degenerative brain disorder
Kuru / laughing disease
Scrapie disease	Falling of wool in sheep
Parkinsonism	No dopamine production
Dementia	Forgetfulness

▢ Viroid:

❖ Definition: Only very low molecular weight RNA

❖ Diseases:

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Potato spindle tuber disease / PSTV
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Chrysanthemum stunt
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Citrus exocortis
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Cucumber pale fruit

Examples

❖ Potato Spindle Tuber Viroid: EU-listed quarantine pathogen of potato → stunting + tuber malformation + cracking

❖ Citrus Exocortis: Stunted growth + reduced yield

▢ Virusoid: Genetic material remains inside living cell

▢ Virion: Completely assembled mature virus particle outside host

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LIFE CYCLE

Table 1: Phage Life Cycle

Type	Also Called	Steps / Key Point
Lysogenic phage	Temperate phage	Adsorption → Penetration
Lytic phage	Virulent phage	Lysis

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PLANT DISEASES CAUSED BY VIRUS

▢ Diseases:

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Tobacco mosaic disease
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Cauliflower mosaic disease
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Dahlia mosaic disease
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Papaya leaf curl / roll
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Potato leaf curl / roll
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Tomato leaf curl / roll
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Yellow vein mosaic of bhindi
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Vein banding mosaic disease of potato
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Bunchy top of banana
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Grassy shoot of sugarcane
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Little leaf of cotton
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Tungro disease of rice

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