ENETIC analyses of crosses of E. coli IS-I2 Hfr x Fhave demonstrated that Gfactors possessed by the donor parent (Hfr) are transferred in a characteristic, oriented, and progressive manner to the recipient (F-) parent ( WOLLMAN, JACOB, and HAYES 1956), and that recombinants segregate only from the Fparent ( LEDERBERG 1956). The transfer of radiophosphorous-containing material (probably DNA) has...