[Gene transfer] How a gene detect where to insert after injected to a nucleus

I have heard of both cases. It can either replace it (mostly in bacteria) or get added randomly in the mix.


The gene usually gets inserted via an enzyme.

So which case it can replace, which case it get added randomly in the mix ?
In the experiment of PhD Yamanaka when he using retro virus to inject 4 gene (Sox2, Oct4, Klf4 and c-Myc), so it replace or added randomly in the mix ? I think it's replaced but as the first question how a gene after injected to a nucleus can detect where to insert/replace itself?

Thank you so much for your answer !

Hi again,

Here's an interesting read (see the attachment).

Gene targeting methods are established for several model organisms and may vary depending on the species used. In general, a targeting construct made out of DNA is generated in bacteria. It typically contains part of the gene to be targeted, a reporter gene, and a (dominant) selectable marker.

To target genes in mice, this construct is then inserted into mouse embryonic stem cells in culture. After cells with the correct insertion have been selected, they can be used to contribute to a mouse's tissue via embryo injection. Finally, chimeric mice where the modified cells made up the reproductive organs are selected for via breeding. After this step the entire body of the mouse is based on the previously selected embryonic stem cell.

To target genes in moss, this construct is incubated together with freshly isolated protoplasts and with Polyethylene glycol. As mosses are haploid organisms, regenerating moss filaments (protonema) can directly be screened for gene targeting, either by treatment with antibiotics or with PCR. Unique among plants, this procedure for reverse genetics is as efficient as in yeast. Using modified procedures, gene targeting has also been successfully applied to cattle, sheep, swine, and many fungi.

The frequency of gene targeting can be significantly enhanced through the use of engineered endonucleases such as zinc finger nucleases, engineered homing endonucleases, and nucleases based on engineered TAL effectors.