For a P1 transduction experiment, an E. coli donor strain with the genotype arg+, ser+, ampR and a recipient strain with the genotype arg-, ser-, ampS were used

The following results were obtained for each marker: Of the transductants selected for arginine, 5% are ser+ and 30% are ampR. Of the transductants selected for serine, 3% are arg+ and 0% are ampR. What is the correct order and relative distance of these three genes on the E. coli chromosome?


The order and relative distance is: ampR-arg----ser. Since amp and ser are never cotransduced, they must be very far apart from each other. Arg and ser are rarely cotransduced, so they must be farther apart from each other than are arg and amp, which are more frequently cotransduced, so they must be fairly close together.

Biology & Microbiology

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