Zygotic induction
Zygotic induction occurs when a bacterial cell carrying the silenced DNA of a
Zygotic induction was discovered by Élie Wollman and François Jacob in 1954.[2] Historically, zygotic induction provided insight into the nature of bacterial conjugation. It also contributed to the development of the early repression model of gene regulation that explained how the lac operon and λ bacteriophage genes are negatively regulated.[3]
Nature of bacterial conjugation
In 1947,
Élie Wollman and François Jacob showed that genes were transferred in a certain order from the Hfr donor cell to the F− recipient cell during mating. The longer that the Hfr and F− cells were in contact, the more genes that were transferred. They did not believe that the entire donor chromosome was typically transferred to the recipient.
Zygotic induction was discovered while the location of prophage λ was being mapped using Hfr x F− matings. When the F− was lysogenic for λ, lysogeny was mapped to the gal locus. However, when the Hfr parent was lysogenic, lysogeny (i.e., the prophage) was not inherited by any of recombinants, which were recovered by growing them as colonies on the appropriate agar medium. The reason is that transfer of the λ prophage into the F− recipient was accompanied by immediate induction of bacteriophage production within the F− cell. Subsequent lysis of this "zygote" released the new bacteriophage particles. If mating terminated before the prophage was transferred, phage was not produced, and recombination proceeded in the zygote. These observations provided evidence that genetic markers was transferred in one direction during conjugation, from the Hfr to F− cell. These experiments also showed that Lederberg's model was incorrect since zygotic induction would have prevented any recombinant from forming had all of the chromosome from the Hfr cell were to be transferred to the F− cell.[7]
References
- ^ Griffiths AJ, Miller JH, Suzuki DT, Lewontin RC, Gelbart WM. "An Introduction to Genetic Analysis". NCBI Bookshelf. Retrieved 7 November 2016.
- ISBN 978-0879693503.
- ISBN 978-0879693503.
- S2CID 1826960.
- ISBN 978-0879693503.
- S2CID 33350056.
- PMID 13433587.