Table of Contents
Biol 568 Advanced Topics in Molecular Genetics
Chapter 11: Phage Strategies
PPT Slide
Survival Strategies
PPT Slide
Lytic cycle or Lysogeny
Extrachromosomal Genomes
Independent Genetic Units in Bacteria
PPT Slide
Lytic Cycle
Lytic Development
Lytic Cycle
Lytic Cycle
Lytic Development: Cascade of regulator genes
Lytic Cycle
Control at initiation of txn
Control at termination of txn
Phage T7; cascade of gene expression
Functional clustering of phage T4 genes
T4 genes; two general groups
T4 gene expression
Lambda phage; lytic cascade & lysogeny
Phage lambda early genes
Phage lambda delayed early genes
Phage lambda delayed early genes
Map of lambda phage
Lambda phage genes are organized in two transcription units
Stages of gene expression
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Lambda phage
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Lambda phage regulatory region
Lambda phage control regions
cI expression
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Lysogeny is maintained by an autogenous circuit
cI is required for initiation at PRM
Autogenous circuit
The immunity region of lambda phage
The immunity region: repressor & operators
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Repressor Binding
Repressor subunit
Repressor functions as a dimer
Repressor
Repressor cleavage induces lytic cycle
Repressor cleavage induces lysogeny
Repressor Binding
Repressor: helix-turn-helix motif
Repressor binding to the operator
The operator is a palindrome
Binding specificities
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l repressor makes an additional contact
l repressor and Cro protein
l repressor and Cro
The operators; three repressor binding sites
The operators; three repressor binding sites
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l repressor binds to DNA cooperatively
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Cooperative binding
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cII interacts with RNA pol. at PRE
Expression from PRE
cII contacts the region at -35
Positive regulation influences RNA polymerase
Lysogeny requires several events
Lysogeny
cII
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Cro
How does Cro achieve its functions?
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Cro represses txn at PRM, PR & PL
PPT Slide
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Lysogeny & Lytic cycle
Lysogeny-Lytic cycle transition
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