The Life Cycle of T4 - Part 2

The Life Cycle of T4 - Part 2

Take me back to Part 1.....or to some Phage Lab Experiments

  1. The T4 Genetic Clock
    (Here begins our first encounter with how a 'clock' can be genetically encoded. As the course progresses, several other ways of encoding clocks will be encountered.)

    1. Early genes

      1. Host transcriptase: a quaternary protein: (alpha)2,beta,beta“,sigma

      2. Immediate Early
      3. Delayed Early
        1. Production of alpha“,beta““, and sigma“

    2. Intermediate (or Quasi-late)
      1. Transcriptase: (alpha“)2,beta,beta““, sigma“

      2. Production of x, y, and z

    3. Late
      1. Transcriptase: (alpha“)2,beta,beta““, sigma“: x,y,z

      2. Requirement for nicks in newly synthsized DNA

  2. Capsomer production and assembly

    1. Baseplate assembly - 15 gene products

    2. Tail tube assembly - 4 gene products

    3. Shell of head - >10 gene products
      1. Making of the subunits
      2. Packing of the head with DNA

    4. Head combines with tail - spontaneous reaction

    5. Tail fibers attached - 4 to 5 gene products

  3. Phenotypic mixing (See figure below)

    1. Relatedness of T2 and T4
      1. Antisera production
        • normal polyclonal production
        • monoclonal production
          • asceptic methods
          • ascites fluids
      2. Cross-reacting material (crm = "crim")

    2. Simultaneous infection of E. coli with both T2 and T4

      1. High m.o.i.
        1. yields phenotypic mixing

        2. half of T4 genomes escape anti-T4 serum
        3. half of T2 genomes escape anti-T2 serum
      2. Low m.o.i.
        1. few mis-wrapped virions
        2. almost all virions susceptible to antisera of same type.

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