title: Insertion of the tetracycline resistance translocation unit Tn10 in the lac operon of Escherichia coli K12.
abstract: The majority of TN10 insertions in the lacZ gene of Escherichia coli occurred in a small region of the promoter distal part of the gene. The resulting mutations were polar on lacY and reverted to Lac+ at a frequency of 10(-8). None of the revertants were Tcr. Furthermore Lac+ Tcr revertants could not be selected directly. Relief of polarity revertants of the lacZ::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.
mesh_terms: D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005696:Galactosidases / Q000378:metabolism; D005796:Genes; D007785:Lactose / Q000235:genetics*; D009154:Mutation; D009876:Operon; D011815:R Factors; D011995:Recombination, Genetic; D013752:Tetracycline / Q000494:pharmacology; D014178:Translocation, Genetic
chemical_list: D005696:Galactosidases; D013752:Tetracycline; D007785:Lactose