Summary
The majority of Tn10 insertions in thelacZ gene ofEscherichia coli occurred in a small region of the promoter distal part of the gene. The resulting mutations were polar onlacY and reverted to Lac+ at a frequency of 10-8. None of the revertants were Tc4. Furthermore Lac+ Tcr revertants could not be selected directly.
Relief of polarity revertants of thelacZ::Tn10 mutants were formed at a frequency of 10-5–10-4. Most resulted from a deletion event internal to the transposon which removed the Tcr genes and the putative transcription terminator. It is postulated that a fragment of Tn10 remains at the original insertion point to cause a revertible Lac- mutation.
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Foster, T.J. Insertion of the tetracycline resistance translocation unit Tn10 in thelac operon ofEscherichia coli K12. Molec. Gen. Genet. 154, 305–309 (1977). https://doi.org/10.1007/BF00571287
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DOI: https://doi.org/10.1007/BF00571287