Retroviral Bacteriophages


"Normal" bacteriophage life cycle:

  • lysogenic cycle
    . . -phage DNA inserted into host bacterium chromosome
    . . -bacterium replication replicates both host and phage DNA
    . . -mitosis produces 2 daughters with phage DNA
    . . . phage DNA propagated over generations of host
    . . . by unknown mechanism, phage DNA becomes lytic
  • lytic cycle
    . . -bacteriophage DNA replicates repeatedly
    . . -bacteria ribosomes recruited to manufacture phage proteins
    . . -phage proteins and DNA are assembled into new phages
    . . -bacterium undergoes lysis, releasing multiple phages.
    Retrovirus
  • has RNA not DNA
  • part of retrovirus mRNA codes for reverse transcriptase
    . . . which inserts DNA sequence coding for retroviral RNA
    . . . subsequent replication and mitosis in host propagates phage DNA
  • when viral DNA becomes lytic, retroviruses reproduced.
  • host bacterium has DNA code for reverse transcriptase
    . . . and can evolve by Lamarckian processes
    . . . Develops resistance to antibiotics

    Ah ha! we have a model for the insertion of genes into genomes.
    . . . which is plot material...



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    © 2004 Prof. LaFrance, Ancilla College