A substituted sex-factor of Escherichia coli, F′8 gal, was transferred to Proteus mirabilis by conjugation. The DNA of the episome was partially purified from Proteus DNA by preparative equilibrium centrifugation in caesium chloride, and by a bulk method using hydroxyapatite. The buoyant density of the episomal DNA is 1.707, corresponding to a (G+C) content of 47%. By optical renaturation the genetic complexity of the episomal DNA was found to be 76×106 daltons. RNA was synthesized in vitro by using the episomal DNA as template. By hybridizing this RNA with DNA extracted from E. coli carrying F′8 gal, it is shown that the number of copies of the episome per replicating chromosome is close to two during exponential growth. The episome makes up about 4.4% of the total DNA of the growing cells. The activities of galactokinase and galactose 1-phosphate uridylyl-transferase in cells with and without episomal and chromosomal gal genes were found to be proportional to the number of gal genes present, when the cells were induced with d-fucose, but not when they were induced with d-galactose.
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January 1971
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Research Article|
January 01 1971
The number of sex-factors per chromosome in Escherichia coli
R. Frame;
R. Frame
1Department of Genetics, University of Edinburgh, Edinburgh 9, U.K.
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J. O. Bishop
J. O. Bishop
1Department of Genetics, University of Edinburgh, Edinburgh 9, U.K.
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Publisher: Portland Press Ltd
© 1971 The Biochemical Society
1971
Biochem J (1971) 121 (1): 93–103.
Citation
R. Frame, J. O. Bishop; The number of sex-factors per chromosome in Escherichia coli. Biochem J 1 January 1971; 121 (1): 93–103. doi: https://doi.org/10.1042/bj1210093
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