The correct gene order is : leu+ trp+ met+ . This is because in all recombinant strains produced from cross between Hfr and F- strains exhibited leu+ first, then trp + and met+ . The most closely linked genes are trp + and met+. Solution The correct gene order is : leu+ trp+ met+ . This is because in all recombinant strains produced from cross between Hfr and F- strains exhibited leu+ first, then trp + and met+ . The most closely linked genes are trp + and met+..