Question

Whats the difference between DNA transformation of a bacterial plasmid with a gene for ampicillan AND transforming E.Coli cells os that they take up a plasmid?

Answer 1

When you transform a bacterial plasmid you insert a gene INTO the plasmid. so you cut the plasmid with restriction enzymes AND you cut the ampicillian-resistance gene from a source, which could be a resistance plasmid discovered in another organism. Then you work on the endigs, both the gene's and the plasmid's, to obtain complementary endigs. at last you have to use DNA ligase to join the endings. It is to say, you created a genetically engeneered plasmid. you put a gene (in this case ampicillan-resistant gene) into a plasmid which previously didn't contain it.

Transform a E.Coli cell is something different. E.coli cells can pick up free DNA from the environment though the wall and the membrane if put in particolar condition (competence status). many bacteria become autonomously competent , others, such es E.coli, don't usually become competent for themselves. you have to treat E.coli cells with chemical or physical processes aimed to pierce the wall. then you put the "injured" cells with a plasmid containing the gene (for simplicity let's consider the same amplicillan-resistant gene) and you hope that the plasmid would enter the cell through the holes in the wall. if this happens, the gene will be expressed in the cell once it recovers from the treatment. plasmids can autonomously replicate and be expressed in a cell without being integrated into the cell's genome.

so, in both cases, you will obtain ampicillan-resistant genetically engeneered cells. in the first case the gene is integrated into a previously existing plasmid. in the second case you insert one more plasmid containing what you're interested in.

Answer 2

Ah okay, thanks, good explanation.