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 |
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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 |
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