1. Discovery of recombination (sex) in E. coli -Lederburg and Tatum (1946)

  2. Fertility factors, F+, F-, and Hfr strains

    1. Hayes (1951) - the transfer is not reciprocal (i.e., it is directional).

    2. Conversion of a recipient strain into a donor strain

    3. Conversion occurs at a very high frequency

    4. Discovery of Hfr strains

    5. Basis:

      1. F+ episome (small circular DNA) has the genes for fertility (origins for replication), genes for the sexual machinery, e.g., pilus)

      2. F+ episome can be transferred on its own (conversion)

      3. F+ episome integrates at many places in the circular chromosome to give the various Hfr chromosome.

      4. Integrated F+ episome DNA is transfer last in an Hfr strain.

    6. “sex-duction”

  1. Recombination mapping

    1. Two factor

    2. Three-factor crosses

  2. Even Phage DNA can recombine - Benzer (1961) and T4 phage genetics

    1. Mutations within a cistron can recombine

    2. Fine structure mapping

    3. Genes are not units of recombination

  3. Using phage to map bacterial genes

    1. Integration can be at one site (lambda) or many (mu)

    2. Specialized transduction

    3. Generalized transduction)