By using the process of conjugation to map the order of genes on a bacterial chromosome, an F- bacterial strain with genotypes gal-, leu-, cys-, thr- was used alongside an Hfr bacterial strain with genotypes gal+, leu+, cys+, thr+. The mating was stopped regularly, and the time taken to transfer the donor genes was: gal 10 minutes, thr 6 minutes, cys 3 minutes, and leu 12 minutes. Which gene is located farthest to the leading side of the F factor, which is where transfer originates?