Midterm 2 - Notes 4 (Part 2) Flashcards
What do genus names end in?
-virus
What do family names end in?
-viridae
What do order names end with?
-ales
Viral species
A group of viruses sharing the same genetic information and ecological niche (host)
Where must viruses be grown in?
In living cells
Where are bacteriophages grown?
In bacteria
What do bacteriophages form?
Plaques
Plaques
Are clearing on a lawn of bacteria on the surface of agar
What does each plaque correspond to?
A single virus
- plaque- forming units (PFU)
Where do you grow animal viruses?
In living animal cells
Cytopathic effect
Virally infected cells are detected via their deterioration
- continuous cell lines are used
What are the 3 steps in cell cultures?
- A tissue is treated with enzymes to separate the cells
- Cells are suspended in culture medium
- Normal cells or primary cells grow in a monolayer across the class of plastic container
- transformed cells or continuous cell cultures do not grow in a monolayer
Viral identification (3)
- Cytopathic effects
- Serological tests
- western blotting - Nucleic acids
- RFLPs
- PCR (eg. herpes)
What 2 things must happen in order for a virus to multiply?
- It must invade a host cell
2. It must take over the host’s metabolic machinery
What are the 2 cycles involved with multiplication of bacteriophages?
- Lytic cycle
2. Lysogenic cycle
Lytic cycle
Phage causes lysis and death of the host cell
Lysogenic cycle (3)
- Phage DNA is incorporated in the host DNA
- Phage conversion
- host cell inhibits new properties - Specialized transduction
- when the host cell replicates its chromosomes is also replicates prophage DNA
T-Even Bacteriophages: The Lytic Cycle stages (5)
- Attachment: phage attaches by the tail fibres to the host cell
- Penetration: phage lysozyme opens the cell wall
- tail sheath contracts to force the tail core and DNA into the cell - Biosynthesis: production of phage DNA and proteins
- Maturation: assembly of phage particles
- Release: phage lysozyme breaks the cell wall
–> leads to assembly of the components for a new virus (eg. tail fibres)
Lysogeny
Phage remains latent
What are the 6 possible stages of lysogenic cycke stages?
- Phage attaches to host cell and injects DNA
- Phage DNA circularizes and enters lytic cycle or lysogenic cycle
3a. New pahge DNA and proteins are synthesized and assembled into virions
4a. Cell lyses, releasing phage virions
3b. Phage DNA integrates within the bacterial chromosome by recombination becoming a prophage
4b. Lysogenic bacterium reproduces normally
Lysigenic stages
Is when the virus DNA is incorporated into the host cell
- will continue to replicate but may exercise and re-enter the lytic cycle
Specialized transduction (2)
- Specific bacterial genes transferred to another bacterium via a phage
- Changes genetic properties of the bacteria
What are the 6 stages in specialized transduction?
- Prophage exists in galactose-using host
- containing the gal gene - Phage genome excises, carrying with it the adjacent gal gene from the host
- Phage matures and cell lyses, releasing phage carrying gal gene
- Phage infects a cell that cannot utilize galactose
- lacking gal gene - Along with the prophage, the bacterial lag gene becomes integrated into the new host’s DNA
- Lysogenic cell can now metabolize galactose
Comparing bacteriophage and animal viruses; attachment
B = Tail fibres attach to the cell wall proteins A = Attachment sites are on the plasma membrane and glycoproteins
Comparing bacteriophage and animal viruses; Entry
B = Viral DNA is injected into host cell A = Capsid enters by receptor mediated endocytosis or fusion
Comparing bacteriophage and animal viruses; uncoating
B = Not required A = Enzymatic removal of capsid proteins
Comparing bacteriophage and animal viruses; biosynthesis
B = In cytoplasm A = In nucleus (DNA virus) or cytoplasm (RNA virus)
Comparing bacteriophage and animal viruses; chronic infection
B = Lysogeny A = Latency: slow viral infections; cancer
Comparing bacteriophage and animal viruses; release
B = Host cell is lysed A = Enveloped viruses bud out; nonenveloped viruses rupture plasma membrane
What are the 6 steps in multiplication of animal viruses?
- Attachment: viruses attach to the cell membrane
- Entry by receptor-mediated endocytosis or fusion
- Uncoating by viral or host enzymes
- Biosynthesis: production of nucleic acid and proteins
- Maturation: nucleic acid and capsid proteins assemble
- Release by budding (enveloped viruses) or rupture
Where do DNA viruses replicate their DNA?
In the nucleus of the host using viral enzymes
Where do DNA viruses synthesize capsid?
In the cytoplasm using host cell enzymes
What are the 7 stages of replication if DNA-containing animal viruses?
- Attachment: virion attaches to host cell
- Entry and uncoating: virion enters cell, and its DNA is uncoated
- A portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins
- Biosynthesis: viral DNA is replicated and some viral proteins are made
- Late translation: capsid proteins are synthesized
- Maturation: virions mature
- Release: virions mature
