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28 Cards in this Set
- Front
- Back
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Viral Replication
One Step Growth Curve What is it? |
Growth of the Bacteriophage over time, usually using Plaque Forming Units (PFUs)
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Viral Replication
One Step Growth Curve Steps |
1. Adsorbtion- attachment of virus to bacterium
2. Eclipse- infectivity of virus disappears 3. Maturation- Assembly of virions |
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Lytic vs Lysogenic
What are the two and what is the difference? |
Lytic Lifecycle - A virus may infect a cell and rapidly replicate, quickly destroying the cell
Lysogenic Lifecycle - Virus may integrate its genome into the host. The viral genome is replicated along with the host, but the majority of viral proteins are not expressed (Temperate phage = living together) These are two paths an infected cell can take. Or it can go through both. |
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Viral Replication
Bacteriophages Steps |
1. Attachment
2. Penetration 3. Replication 4. Biosynthesis 5. Assembly of Capsids 6. Release of mature virons |
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Viral Replication
Attachment |
Interaction between bacteriophage and receptor. Receptor may consist of proteins, glycoproteins, carbohydrates.
Ex. 1. Phage T1 binds an iron uptake protein 2. Phage lambda binds a maltose uptake protein |
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Viral Replication
Attachment Susceptible |
Cells where attachment can occur.
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Viral Replication
Penetration |
entry of bacteriophage genome in cytoplasm. Capsid remains attached to outside of cell.
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Viral Replication
Penetration Permissive |
Cells which allow viral replication
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Viral Replication
Restriction What is it? How do Cells protect their own DNA? |
To cleave viral DNA at specific sites.
The host organism can prevent damage to its own DNA through glycosylation and methylation of the genome. These prevent attacks or will prevent attachment of the restriction enzyme to attack. Viral DNA also uses these two methods to prevent restriction |
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Viral Replication
Eukaryotic Viruses (Animals) Stepts |
1. Attachment - Virion attaches to membrane receptor
2. Entry - Fusion of virion and membrane 3. Uncoating - Host enzymes release viral genome from capsid 4. Genome Replication 5. Biosynthesis - Genome directs cellular enzymes, Viral proteins, Viral replication 6. Encapsidation - Viral genome encapsidated; Coat protein assembles around Nucleocapsid; Replicases, Reverse Transcriptases present in nucleocapsid 7. Escape - Virus buds off (envelope virus) or lysess |
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Virus Replication
Where does replication occur in the cell? Bacteriophage v. Eukaryotic |
Bacteriophages replicate entirely in the cytoplasm. Animal viruses utilize various cellular compartments during their replication schemes.
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Virus Replication
Where does replication occur in the cell? Eukaryotic |
1. DNA replication and transcription often occur in the nucleus.
2. Translation occurs in the cytoplasm and often involves cytoplasmic and secretory proteins. 3. Genetic information for Poly A tail is encoded in gene. |
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Bacteriophage T4
Make-up |
1. Complex virus
2. DS DNA genome (linear) a. Circularly permuted b. Terminal repeats c. 168,903 base pairs d. 5 hydroxymethylcytosine (instead of cytosine) (i) Glucosylation of residue inhibits restriction endonucleases 3. Host E. coli 4. Lytic infection |
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Bacteriophage T4
Attachment |
1. Tail fibers have weak interactions with LPS on cell surface
2. Rearrangement of base plate proteins 3. Short tail fibers bind irreversibly 4. Tail contraction a. gp5 punctures membrane b. Lysozyme domain of gp5 degrades peptidoglycan c. Plasma membrane punctured |
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Bacteriophage T4
Entry |
T4 chromosome enters cytoplasm
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Bacteriophage T4
Replication Scheme Early/Middle Genes |
1. Host RNA Polymerase reads viral genes using host Sigma factor
2. Sequential covalent modifications (ADP-Ribose) to α subunit favor viral genes 3. Anti-sigma factor shuts down host RNA synthesis 4. Enzymes for synthesis of 5 hydroxymethylcytosine and glucosylation 5. Degradation of cytidine tri-phosphate 6. MotA protein binds viral DNA attracts host RNA Polymerase to Middle genes |
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Bacteriophage T4
Replication Scheme Late Genes |
1. Require gp55, a phage T4 sigma factor
2. Structural proteins (head and tail) 3. T4 Lysozyme aids in escape |
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Bacteriophage M13
Make-up |
1. Filamentous
2. Single stranded circular DNA genome 3. 6407 nucleotides 4. Infects E. coli 5. Escapes cell without lysis (Fig.16.5) |
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Bacteriophage M13
Attachemnt |
C-Protein --> PIII attaching to the F Pillus and To1A Proteing
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Bacteriophage M13
Assembly |
1. Coat protein embedded in plasma membrane
2. Encapsidation occurs as viral genome moves through plasma membrane |
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Bacteriophage M13
Biotechnology Applications |
1. Intergenic region allows for cloning
2. Phage Display Library utilizes hybrid of coat protein |
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Tobacco Mosaic Virus
Make-up |
1. Helical
2. Single stranded (+) RNA genome linear 3. 6395 nucleotides 4. Infects tobacco, tomato and other plants 5. Mechanical inoculation |
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Tobacco Mosaic Virus
Genome (Only codes four) |
1. Methyltransferase (MTH) - Helicase activity, Synthesizes 5’ cap on viral mRNA
2. Replicase (RNA Dependent RNA Polymerase) - Onoy when ribosome accidently reads through of stop codon on MTH produces MTH-RNP polyprotein 3. Movement Protein - Cell to cell movement via plasmadesmata 4. Coat Protein |
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Tobacco Mosaic Virus
Synthesis Details |
1. Replication of genome occurs in cytoplasm - Involves synthesis of (-) genome serving as template for (+) genome synthesis
2. Coat Protein and Movement transcribed from (-) template - Subgenomic RNA |
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Influenza Virus
Make-up |
1. Envelope virus
2. Polymorphic symmetry 3. Infects humans, birds 4. Airborne transmission 5. Genomome - 8 Segments of linear (-)ssRNA |
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Influenza Virus
Envelope Proteins What are they? |
1. Hemagglutinin - Binds sialic acide during attachment
2. Neuramindase - Cleaves sialic acid and facilitates viral escape and movement |
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Influenza Virus
Influenza Life Cycle |
1. Attachment: Viral Hemagglutinin attaches to sialic acid residues on host cell
2. Entry: Endocytosis of entire virion particle into cytoplasm 3. Uncoating: Acidification of endosome causes Hemagglutinin rearrangement that fuses viral membrane with endosome. Viral genome enters cytoplasm. 4. Genome Replication: Occurs in cytoplasm. RNA Dependent RNA Polymerase that is encapsidated with viral genome performs this function. (-) genome generated in large amounts. 5. Biosynthesis: Template for transcription enters host cell nucleus. Transcription of viral genes occurs in nucleus. Cap snatching favors translation of viral mRNA. Translation of envelope proteins occurs in the Rough Endoplasmic Reticulum. Translation of other viral genes occurs in the cytoplasm. 6. Assembly: Occurs at cell surface. 7. Escape: Via budding of virion particles from cell. Neuraminidase plays role by cleaving sialic acid residues. |
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Influenza Virus
Treatments |
1. Amantadine – inhibits viral ion channel proteins. Inhibits uncoating.
2. Zanaminivir – neuraminidase inhibitor. Inhibits viral release. |
