Topic 5 Flashcards
Who founded viruses?
Dimitri inv…
Who showed yellow fever was a virues
Walter reed
Who coined the term plaque and found bacteriophages
Felix d’…
What are bacteriophages and what a good fact on them
There are viruses that eat bacteria , they are the most abundant on earth
Why are viruses not considered alive
They are not considered alive bc they need a host self to be able to replicate and they have no
Metabolism
What are viruses
They are a small subcellular partice that requires a host to replicate
Between pro and eukaryotes and viruses who is the smallest
Viruses
What is the structure of a virus (whats in a virus)
A virus can have either sigular or linear RNA OR DNA Genome
With a protein shell surrouding it called capsid
And same may have an envelope surrounding the capsids
Where can the viruses get its envelope
It can get it envelope from the host cells membrane , golgi app, ER or nucleus
What is a nucleocapsid
Its rhetorical Genome + capsid
What is the possivle size of virus
its can be 10 nano metres -100 nanometers
What are the three big virues exception
Mimivirus 400 nanomemteres ,pandroaviruses 1micro , mega viruses
How many shapes can capside comes as ?
Helical icoshedral or irregular like bacteriophages
There are 3 proteins are each icosohedreal face and there are 20 faces meaning there are 60 capsoemrec
What is the duty of a capsid,
To protect the rna or dna through processes
What are the 6 steps for viral replication
Adhere (stick to host cell)
Enter
Uncoat( release genome)
Synthesis (replicate genome)
Assembly( put together new viral particle)
Exit
For an animal cell what are the two ways a virus can enter
Endocytosis and membrane fusion
What are the steps for endocytosis for an unenvelope membrane ?
- Virusues attaches to cell receptors
- Endocytosis is initiated
- An endosomes forms with the virus inside
- The nucleocapsid enters the cytoplasm and release tbe genomes
What are the steps for membrane fusion of an enveloped virus
- Virus attaches to cell receptors
- A change in the attachement proteins let the receptor initiate membrane fuction
- The virus and evelops and plasma membrane of host cell fuses
- The nucleocapsid enters the cytoplasm and the genomes are released
What are the 4 steps for endocytosis of and envelopes virus?
- Virus attaches to cell receptor
- Endocytosis is initiated
- An endosomes forms with virus inside
- The low ph in the endosome initiates fusiin between the endosomes membrane and the virus and the nucleocapsid is released
What is need for a virus to enter a plant ?
Damage is needed to the plant tissue to open the cell wall
What are the steps for a bacteriophage to enter a bacterial cell
- Tail fibers attach to receptors
2.Change in tail fibers allow base of tail to get into contact with surface of host cell - Rearrangements of tail proteins allow the tube proteins to enter the cell wall through to the membrane
- When bacteriophage get in contact with the membrane , DNA IS RELEASED
What is the lytic cycle of bacterial replication
Its is when the viral enter , replicates and always ends up killing the host
What is the temperate page aka lysogenjc cycle
Where a bacteriophage enters and cell and stay untill conditions gets bad then kills the cell
Can either is a prophage or lytic
What is prophage
When a virus is in the cell but doesnt kill the host right away
What are the three therories called that explain where viruses come from ?
Regressive, coevelution ,progressive
What is the coevolution theory
The co evolution theory proposes that microbes and viruses originated around the same time as each other and kinds like “grew up with each other “ and co evoluted .
What is the progressive theory ?
The progress theory is the theory where viruses came from a genetic material that had the sbioity to self replicate and transfer semi automously
What is the regressive theory
The theory is that i s orginated a an alive organism but them turned into a particle
What are the 4 steps to cultivating bacteria ?
- Get a small sample of your bacteria with a suspected virus and pour it into a phage sample
- Pour sample mixture into molten nutrient agar and mix
- Pour same mixture with agar into an incubutar with nutrient base agar and wait for it to solidify
- Check for plaque on plate
What is differential centtrifugation
- You centrifuge it at a low speed and watch large particles fall and transfer to another tube
- You centrifuge it at medium speed and watch small broken particles fall transfer
- You centrifuge it at high speed and virus pellet should be separated
What is gradient centrifuge
- Fill a tube with different levels on concetrations of sucrose
- Put mixture with suspected virus on top
3.viruses should be separated on band of concentration
What 2 things help purify a virus
Differential and gradient centrifugal
What are the 4 viral quatification ?
Plaque assay
Endpoint assay
Hemmaglutination
Direct count
What is a direct count quantification
Direct count helps get a accurate count of the total viral particles it doesn’t tell between non infectious or infectious
You can only use am EM with a known volume
What is hemoglutination?
Using RBCs when a rbc is in the presence of a virus they stick together , it doesn’t provide an accurate count and cant tell between non infectious or infectious
What is plaque assay ?
Plaque assay is used for counting accurately how many infections particlds there are by the clearing zones by cultivating bacteria
What is endpoint assay ?
A stas graph thats tells you the TCID 50 (tissue cuture infectious dose) and the LD50 ( lethal does 50)
Basially how much concetration you need for a response
What are 3 things that make viroids, viral-like
Being small
Causing disease in plant
Having only RNA
What are 3 things that makes proins viral-like
Caused mad cow disease
Has only protein
Has a different infectious agent
