Austin Taylor and Edward Adelberg isolated some new strains of Hfr cells that they then used to map

several gnes in Escherichia coli by using interrupted conjugation (A. Taylor and E. A. Adelberg. Genetics 45: 12331243). In one experiment. the researchers mixed cells of Hfr strain AB-312, which were xyr mtl mar met* and sensitive to phage T6, with F- strain AB-531. which was xyr mt'- mat- met- and resistant to phage T6. The cells were allowed to undergo conjugation At regular intervals, the researchers removed a sample cells and interrupted conjugation by killing the Hfr cells with phage T6. The F- cells, which were resistant to phage T6, survived and were then tested for the presence of genes transferred from the Hfr strain. The 200 150 results of this experiment are shown in the graph below. On the basis of these data, give the order of the xyl, mff. mal, and met genes on the bacterial chromosome below and the minimum distances between them in minutes. The origin Of transfer is represented by the red triangle. The distances between genes are not to scale. The circle represents the bacterial chromosome and the lines through the circle are gene locations. 50 tntl+ 0 20 40 60 80 100 Time of sampling (minutes)