Austin Taylor and Edward Adelberg isolated some new strains of Hfr cells.

16. Austin Taylor and Edward Adelberg isolated some new strains of Hfr cells that they then used to map several genes in E. coli by using interrupted conjugation (A. L. Taylor and E. A. Adelberg. 1960. Genetics 45:1233-1243). In one experiment, they mixed cells of Hfr strain AB-312, which were xyl mtl mal met and sensitive to phage T6, with F strain AB-531, which was xyl mtl mal met and resistant to phage T6. The cells were allowed to undergo conjugation. At regular intervals, the researchers removed a sample of 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 results of this experiment are shown in the accompanying graph. On the basis of these data, give the order of the xyl, mtl, mal, and met genes on the bacterial chromosome and indicate the minimum distances between them. (8 pts) 200 mal+ 150 100 met+ 0 8 Time of sampling (minutes)