In the laboratory, recombinant plasmids are commonly introduced into bacterial cells by: A) electrophoresis-a gentle low-voltage gradient draws the DNA into the cell. B) infection with a bacteriophage that carries the plasmid. C) microinjection. D) mixing plasmids with an extract of broken cells. E) transformation-heat shock of the cells incubated with plasmid DNA in the presence of CaCl₂.

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Transformation is the most common method used in laboratories to introduce recombinant plasmids into bacterial cells. The plasmid DNA is mixed with the bacterial cells in the presence of CaCl2, and then a heat shock is applied. This creates temporary pores in the bacterial cell wall, allowing the plasmid DNA to enter the cell. Once inside, the plasmids replicate independently of the bacterial chromosome.

In the Laboratory, Recombinant Plasmids Are Commonly Introduced into Bacterial