By conducting conjugation experiments between Hfr and recipient strains, Wollman and Jacob mapped the order of many bacterial genes. Throughout the course of their studies, they identified several different Hfr strains in which the F-factor DNA had been integrated at different places along the bacterial chromosome. A sample of their experimental results is shown in the following table:

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Hfr Order of Transfer of Several Different Bacterial Genes Strain First Last H thr leu azi ton pro lac gal str met 1 Lev thr met str gal lac pro ton azi 2 pro ton azi leu thr met str gal lac 3 lac pro ton azi leu thr met str gal 4 met str gal lac pro ton azi leu thr 5 met thr leu azi ton pro lac gal str 6 met thr Leu azi ton pro lac gal str 7 ton azi leu thr met str gal lac pro