The five E.coli Hfr strains are having different F plasmid insertion points and orientation. All the strains have the same order of genes on the E.coli chromosome. The orientation of the F factor determines which gene enters the recipient cell first. Thus, gene closest the terminus enters last.
Therefore, the last gene to be transferred into the F‾ from each of the five Hfr strains is thi 2 lac 1 pro 3 gal 312 gly.