How are plasmid vectors used to transfer genes?
The plasmid with the cloned insulin gene can now be transformed into competent bacteria hosts (or yeast if desired, however it will not be as efficient). Competence describes the ability of bacteria to take up DNA from its surroundings. The most commonly used host, E. coli, are artificially made to be competent by treatment with a high concentration calcium solution in a cold environment, while others, such as B. subtilis, are naturally competent. All bacteria can be made competent with electroporation but E. Coli is most often used because of its easily satisfied nutrient requirements and very short generation time. The plasmid and competent E. coli is placed together in a cold environment to initiate the uptake of the plasmid into E. coli cells. The mixture is then heat shocked and bacterial growth medium with the necessary selection agent is added to start the incubation process. If the selection marker on the plasmid is an antibiotic resistance gene, for example ampicillin resistan
