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Cheatography

The Viral World-L2 Cheat Sheet (DRAFT) by

Biology Lecture 2

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Common Features of a Virus

1. Genome
- Could be ssDNA, dsDNA, dsRNA, ssRNA
- Viruses are particles and there is a question about if they are living or non-living (need a host cell for reprod­uction)
- Our genome is DNA, viruses can harm different types
--> Always a nucleic acid
What does the genome do?
- Codes for proteins to run the virus
--> genome is the smallest
2. Capsid
- a virally coded protein coat, shell, or sheath that surrounds the nucleic acid
Capsid= protein coat surrou­nding genome
Protects genome from breakdown and facili­tates entry
Some viruses have membrane

Virus Diversity

Rod
- RNA
- Capsomere of capsid
ex: Tobacco mosaic virus
Simplest virus
Adenov­iruses
- Capsomere
- DNA
- Glycop­rotein
- Cause us to get sick
Circle Virus
- Membranous envelope
- RNA
- Glycoprotein
- Capsid
ex: Influenza Viruses
- Affect animals= have membrane around capsid
Moon Landing Shaped One
- DNA
- Tail sheath
- Head
- Tail fiber
ex: Bacter­iophage T4
- Phages are viruses that collect bacteria
--> bacter­iop­hages

Genome of HIV Virus

gag
Components of capsid
- Matrix
- Capsid
- Nucleocapsid
- Vpr-bi­nding protein
pol
Proteins required for reverse transc­ription and integr­ation into host DNA
- Protease
- Reverse transcriptase
- Integrase
env
Surface Proteins
- Surface glycoprotein
- Transm­embrane glycop­rotein
Infection Cycle
Infects human white blood cells
- Immune System deficiency
 

Viral Genome Classi­fic­ation

Virus Classes
Class 1
> Double­-St­randed DNA (+)
Class 4
> Single­-St­randed RNA (+)
Class 5
> Single­-St­randed RNA (-)
Class 6
> Single­-St­randed RNA (+)
--> SPECIAL "­retro virus"
Use genome (DNA and RNA) of virus to classify the bacteria
Must ask:
- How is genome made? Poly. used?
- How is the mRNA made? Poly. used?
- Are the poly derived from the host or virus genome?
D.S. DNA Viruses
- Genome: D.S. DNA (what comes into host)
--> DdDp needed for virus (host has this)
- mRNA: D.S. DNA --> mRNA
--> DdRp (already has this in host)
RNA
- ss(+) RNA virus=> many bacteria phages
- Genome­:ss(+) RNA=>template(-)RNA=>(+)RNA
--> RdRp: has to be virally encoded. Does not have to be carried in by virus since (+) RNA can be read by mRNA
ss(-)R­NA=­>(+­)ss­RNA­=>(­-)ssRNA
- RdRp: has to be brought in by virus
Retrovirus
- even though they are (+) RNA they dont follow pattern.
- Be integrated into host genome and replicate the provirus with it
(+)ssR­NA=­>DN­A=>­Protein
> Reverse transc­riptase carried by virus (after +ssRNA)
> DNA integrated interm­ediate host genome

Influenza Virus

H and N
> glycop­roteins on the surface of the glycoprotein
> HA- 16 common variants of the protein
> NA- 9 common variants of the protein
(-) ssRNA virus with a genome with 8 segments
> Newly released influenza viruses will be geneti­cally hetero­genous enabling a high rate of evolution
> HA and NA may not be detectable by our immune system due to antigenic drift
--> Enters via fusion
--> Carries own polyperase
---> doesnt have proofr­eading mechanism
high mutation rate
Viral reasso­rtment may lead to antigenic shift (a new influenza subtype)
- different strains for humans and animals

Basic Viral Infection Cycle

1. Entry and uncoading
2. Replic­ation
3. Transc­ription and manufa­cture of capsid proteins
4. Self-a­ssembly of new virus particles and their exit from the cell
Phages are the best understood of all viruses
Entry: Mechanism to the virus that attaches to the host cell and into the cytoplasm
- Viruses that have membranes can be receptor mediated (*endo­cyt­osis)
- Bacteria phage injection genome
--> can be replic­ated, always ends up in cell bursting
Flu Virus= membrane fusion membranes fuse together and go into cell
Recept­or-­Med­iated Mechanism
Replic­ation= DNA replic­ation. Every time a cell divides
Central Dogma
-DNA
--Transcription (DdRP RNA Polymerase)
-RNA
--Translation(Ribosomes, tRNA...Always sue ribosomes from the host)
-Protein
DdDp ==> DNA dependent DNA polymerase