Question

While creating the first Recombinant DNA why was it necessary for linking the gene of interest with the plasmid of Salmonella typhimurium when E coli already have their own plasmids??? Why can't we directly introduce our gene of interest in ecoli medium so that our gene of interest is directly in the plasmid of ecoli itself??

Answer 1

When recombinant technique is done the plasmid has to be first taken out from the bacteria and introduce a gene of interest .This is recombinant DNA plasmid.Such a plasmid is reintroduced in to bacterial cell again to make more copies of the gene of interest.
When it all started by the scientist Stanley Cohen and Boyer , they must have done lot of trials in different ways.
They have succeeded in introducing plasmid of S.typhimurium in E.coli.That is what is reported in the text book.
Plamid can be introduced in to any bacterium.But when it all started the technique is not that well understood.
So what the scientists did and how they did is written in the text book.