I think it is generally true to say that individual genes don't work in a vacuum, and neither do the biological mechanisms they encode for, so the transferred DNA would have to contain a suite of co-dependent genes. Admittedly, there is a counter-example in the transfer of genes conferring resistance to a particular pathogen.

I think it is also true to say that convergent evolution often produces results that differ genetically, even though the resulting phenotypes serve the same purpose.

Like this retrotransposon? https://www.theatlantic.com/science/archive/2018/04/the-shel...

Check out these guys: https://en.wikipedia.org/wiki/Transposable_element