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19 Cards in this Set

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Bacteriophage growth
- must be inside cell to reproduce
- one step growth curve
+viral progeny made and released at same time
-Eclipse period
-Latent period
-Rise period
-Burst size
-no intact virons exist
-no viral progeny released yet
-viral progeny released
-# of viruses produced per infected cell
Plaque
-zone of bacterial or cell lysis due to infection by a single viron
-Only formed by viable virus particles
-Plaque Forming Units(number of colonies)
-can be used to obtain pure viral cultures
Bacteriophage Repoduction Cycle
A)Lytic Infection
-cell lysis during virus release
-Virulent Phages
B)Latent Infection
-incorp into host cells chrom
-later reactivated to cause lytic infection
-Temperate phages
Virulent Phage Reproduction
1)Attachment
2)Penetration & Uncoating
3)Replication of Viral NA
4)Synthesis of Viral coat proteins
5)Assembly of Virons
6)Release of Viral Progeny
1) Attachment
-Phages bind to specific receptor sites
-Receptor sites vary among phages
-No receptor no attachment
2) Penetration & Uncoating
-Penetration of viral DNA, and loss of empty capsid
3) Replication of viral nucleic acid
-Virus stops reproduction of cell DNA, RNA, Proteins
-Activation and transcription of early genes
-3 types of early genes
1) enzymes to degrade bacterial DNA
2) enzymes to aid in synthesis of viral DNA
3) Proteins involved in inhibiting bacterial mechs
Synthesis of T4 DNA
-Contains hydroxymethylcytosine (HMC) instead of cytosine
-After DNA synth HMC is glycosylated, protecting the DNA
Replication of ssDNA
-must generate a dsDNA replicative form before replication or transcription can occur
4)Synthesis of Viral Coat Proteins
- Virus-encoded sigma factor directs the reading of the late genes by the cell's RNA polymerse
- Late- transcribed after the phage nucleic acid is replicated
3 Catergories of Late Genes
1)Phage structural proteins
2)Proteins that aid in phage assembly
3)Proteins involved in cell lysis and release of phages
5)Assembly of Virons
-Spontaneous self assembly
1)Head
-Proteins assembled in prohead
-DNA packed into head
2)Tail
-attached to head at collar
3)Tail fibers made & attach to baseplate
-Ends eclipse period
6)Release of Viral Progeny
-Lysis usually
-T4 proteins
+Endolysin (attacks petidoglycan)
+Holin (lesions in cell membrane)
-latent period is 22 mins after infection
B)Temperate Bacteriophages
-Specialized transduction
-Lysogeny
+Non-lytic relationship btwn phage and host
+Intergration of phage genome into host DNA (prophage)
+Lysogens(infected bacterial host)
Lambda repressor
-cI gene product
-Activated= lambda remains prophage
-Inactivated= prophage excises and becomes virulent
+Repair mechs for DNA directly inactivates repressor protein
Cro Protein
-Cro gene product
-Regulates lytic cycle genes
-Blocks synthesis of lambda repressor
Induction
-Activation and excision of prophage
-Triggered by drop in Lambda Repressor
-Virus then enters lytic replication cycle
1)Inductase
2)Excisionase
1)Viral enzyme that catalyzes induction of lamba genome into cell's genome
2)Enzyme that reverses intergration process by binding to integrase