Question

You use à new strain of Hfr E. coli to map several genes by using interrupted conjugation. You mix Hfr cells that are xy/+ mil+ mal+ met+ and sensitive to phage T6. You mix those cells with an F- strain that is xyl- mil- mal- met- and resistant to phage T6 to allow conjugation. At regular intervals, you remove samples and interrupt conjugation. You kill the Hfr cells in each sample by using the T6 phage and plate what's left on various media. The results of the experiment are in the following graph. On the basis of these data, map the xyl, mtl, mal and met genes on the bacterial chromosome and indicate the 4. minimum distances between the genes. 150 100 met' 0 20 40 60 80 100 Time of sampling (minutes)

Answer 1

Mutations at different functional loci that encode a different protein, in bacterial cells infected by both mutants, the wildtype sequences on the chromosome opposite each mutation will overcome the effects of the recessive mutations.

The wild-type gene entering first will able to grow on a media deficient for that gene product and the colonies growing lastly would indicate the gene responsible for that entering last

From the graph, the order genes on the chromosome would be

Mal--Xyl--Mtl--Met