Genetic and Physicochemical Characterization of Escherichia coli Strains Carrying Fused F′ Elements Derived from KLF1 and F57

  1. Neil Willetts* and
  2. Fernando Bastarrachea
  1. 1Departamento de Genética y Biología Celular, Centro de Investigación y de Estudios Avanzados del I. P. N. México 14, D. F. México

Abstract

Although the two F′ elements, F57 (carrying his +) and KLF1 (carrying leu +), cannot normally coexist in the same cell, crosses between RecA- strains of Escherichia coli carrying these two elements gave rise, at a low frequency, to progeny carrying both the his + and leu + markers in an extrachromosomal state. Genetic studies showed that the his + and leu + markers were now linked, and centrifugation studies of F′ DNA isolated from these strains confirmed the presence of a new species of DNA molecule of altered size. It is proposed that the his + and leu + genes in these strains are covalently linked on a single “fused” F′ element.

Footnotes

  • ↵ * Present and permanent address: MRC Molecular Genetics Unit, Department of Molecular Biology, University of Edinburgh, Edinburgh, Scotland.

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  1. PNAS 1972-06 vol. 69 no. 6 1481-1485
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