Abstract
Escherichia coli DNA in the neighborhood of the φ80 attachment site, including the tryptophan operon, an ochre suppressor gene ( su c ) and F lac DNA transposed into the same region, was analyzed. DNA isolated from the transducing phages φ80 pt 1, φ80 pt 0, φ80 dsu c and φ80 d 1 lac was fragmented by shear and fractionated with respect to buoyant density of mercury complexes in cesium sulphate. Bacterial and episomal DNA components were identified by hybridization experiments. A segment containing the tryptophan operon consists of DNA ranging in G + C content from 43 to 57%, and the operator proximal end is richer in G + C. The composition of a segment between su c and att 80 varies in the same range, with an average G + C content of 51%. A segment containing lactose genes is more homogeneous, with an average G + C content of 54%. A portion of F factor, recovered from φ80 d 1 lac, ranges in G + C content from 37 to 52%.
Published Version
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