Boyer and Cohen's goal was to get the plasmids into E. coli. Through a chemical experiment, they mixed the bacteria and the DNA in a mixture of calcium chloride. This mixture was set at a freezing temperature. They later created a "heat shock" by raising the temperature to 42 degrees Celsius and lowering the temperature back down to the freezing temperature. Through this procedure, the bacteria takes in the plasmid DNA. Later the resulting bacteria was placed in an environment with only tetracyline and kanamycin where only the transformed bacteria could thrive. This showed that the bacteria had the two genes needed for them to survive in that environment which were the tet and kan. Some resulted in doubly transformed bacteria. Through this experiment, Boyer and Cohen were able to distinguish between the different plasmids in the colony.
E. coli have adhesion zones where they have lipid molecules with negatively charged phosphates used to repel plasmid DNA. The lowered temperature decreases the movements of the lipids which in turn makes them easier to shield. When the heat shock occurs, the DNA is able to penetrate the adhesion zone.
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