A model for three-point analysis of random general transduction.

INCE the discovery of bacterial transduction ( LEDERBERG, LEDERBERG, ZINDER and LIVELY 1951), it has been recognized that there are two distinct classes: special (MORSE, LEDERBERG and LEDERBERG 1956) and general (ZINDER and LEDERBERG 1952; LENNOX 1955; and JACOB 1955), which involve different mechanisms. In the case of general transduction, the chromosome segments carried by the phages can be obtained either from breaking the bacterial chromosome at fixed points as in the phage P22-Salmonella system (ZINDER and LEDERBERG 1952), or from breaking it randomly as in the phage P1-Escherichia coli system (LENNOX 1955). In the present study, a model is proposed for the random general transduction. The model: The three-point analysis of transduction has been used extensively for defining the linear order of genetic markers (YANOFSKY and LENNOX 1959; GROSS and ENGLESBERG 1959; ADLER and KAISER 1963; FRANKLIN and HOWARD 1965 j GLANSDORFF 1965; SIGNER, BECKWITH and BRENNER 1965; and COZZARELLI and LIN 1966). Twelve measurements in three sets of fours are analyzed (Figure 1 ) . One of the markers carried by the transducing segment is selected, and the other two markers are then analyzed for their origin from either the transduc-