Introduction to Genetic Analysis 164

Introduction to Genetic Analysis 164 - w w w. ANIMATED ART...

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Unformatted text preview: w w w. ANIMATED ART 163 5.2 Bacterial conjugation However, sometimes the exit is not clean, and the plas- mid carries with it a part of the bacterial chromosome. An F plasmid carrying bacterial genomic DNA is called an F 9 (F prime) plasmid. The first evidence of this process came from experi- ments in 1959 by Edward Adelberg and Franois Jacob. One of their key observations was of an Hfr in which the F factor was integrated near the lac 1 locus. Starting with this Hfr lac 1 strain, Jacob and Adelberg found an F 1 derivative that in crosses transferred lac 1 to F 2 lac 2 recipients at a very high frequency. (These transferrants could be detected by plating on medium lacking lac- tose.) Furthermore, these F 1 lac 1 exconjugants occasion- ally gave rise to F 2 lac 2 daughter cells, at a frequency of 1 3 10 2 3 . Thus, the genotype of these recipients appeared to be F 1 lac 1 / F 2 lac 2 . In other words the lac 1 exconjugants seemed to carry an F plasmid with a piece of the donor chromosome incorporated. The origin of thisof the donor chromosome incorporated....
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