Auxotrophic mutations for phenylalnine (phe), tyrosine (tyr), uracil (ura\'), an

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Auxotrophic mutations for phenylalnine (phe), tyrosine (tyr), uracil (ura'), and glycine (gly) are closely linked on the chromosome of E. coli. To resolve the order of the genes, you study cotransduction of the markers by generalized transduction using phage P1. You infect P1 on a wild-type E. coli and then use the resulting progeny phage from that infection to infect a phe tyr ura' gly strain of E. coli. You select 500 ura+ transductants and test them for transduction of the other markers as well, with the following results: Draw the order of the genes as best you can based on the cotransduction data. Do NOT calculate map distances.

Explanation / Answer

According to the number of transductants the order of the genes are: ura-gly-phe-tyr As the highest number of cells have only ura+, we can assume that this is the first gene. The second highest number of transductants show gly+. The third highest number of transductants show phe+. The fourth highest number of transductants show tyr+. As the highest number of cells have only ura+, we can assume that this is the first gene. The second highest number of transductants show gly+. The third highest number of transductants show phe+. The fourth highest number of transductants show tyr+. The third highest number of transductants show phe+. The fourth highest number of transductants show tyr+. The fourth highest number of transductants show tyr+.

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