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15 Cards in this Set

  • Front
  • Back
two criteria for classiying bacteriophages
phage morphology and nucleic acid properties
lytic cycle
-cycle of reproduction for double-stranded DNA phages
-phage life cycle that culminates with host cell bursting, releasing virions
virulent phages
phages that lyse their host dring the reproductive cycle
the one-step growth experiment
-mix bacterial host and phage
-brief incubation (attachment occurs)
-dilute greatly (released viruses cant infect new cells)
-overtime, collect sample and enumerate viruses
adsorption to the host cell and penetration
-receptor sites -->specific RECEPTORS on host to which viruses attach
---> specific ATTACHMENT SITES on each virus
(can be proteins, lipopolysaccharides, teichoic acids)
synthesis of phage nucleic acids and proteins
--->EARLY mRNA synthesis
--->synthesis of proteins that enable T4 to take over the hsot cell
--->phage DNA replication
--->LATE mRNA synthesis (encode capsid proteins and other proteins needed for phage assembly)
how is early mRNA made?
-some by regular host RNA polymerase
-others by modified host RNA polymerase
what are the concatamers in T4 DNA?
long strands of DNA consistnig of several units linked together
T4 proteins that bring about lysis of host
-endolysin: attacks peptidoglycan
-holin: produces lesion in cell membrane
-nonlytic relationship between a phage and its host
-usually involves INTEGRATION of phage genome into host DNA
---->PROPHAGE=integrated phage genome
---->LYSOGENS (lysogenic bacteria)= infected bacterial host
---->temperate phages=phages able to establish lysogeny
-process by which phage reproduction is initiated
-results in switch to LYTIC CYCLE
lysogenic conversion
-change in host PHENOTYPE induced by lysogeny
(ex: modification of Salmonella lipopolysac structure/production of diptheria toxin by corynebacterium diptherieae
lambda phage
-double stranded DNA phage
-temperate phage
-linear genome with cohesive ends
If lambda repressor wins...
-lambda genome inserted into E.coli genome
(integrase:catalyzes integration)
-triggered by drop in levels of lamda repressor
---> caused by exposure to UV LIGHT and chemicals that cause DNA DAMAGE
-excisionase (binds integrase and enables integrase to reverse integration process)