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Alkaline Lysis Theory

Scientists use alkaline lysis to extract plasmid DNA from bacteria for use in genetic experiments. Plasmids are small circular molecules of DNA containing a small piece of genetic code for study.

  1. Why Alkaline Lysis

    • The alkaline lysis protocol consists of a series of solutions added to a bacterial pellet containing plasmid DNA. The increased alkalinity of the solution causes cells to burst. This method of extraction protects the plasmid DNA while destroying the genomic DNA and denaturing cellular proteins to providing scientist with a relatively pure sample.

    SDS and NaOH

    • Alkaline describes the two major chemicals used to cause the lysis of individual cells. Sodium dodecyl (lauryl) sulfate (SDS) is a detergent that destabilized the cell by creating holes in the cellular membrane. Sodium Hydroxide (NaOH) adds in breaking down the cell wall causing the cell to disintegrate and release its genetic material into solution.

    Why Plasmid DNA Survives

    • An additional property of NaOH in the alkaline lysis protocol is to disrupt the hydrogen bonding between DNA base pairs. This denatures genomic DNA and plasmid DNA to single strands. The addition of potassium acetate to the solution neutralizes the alkalinity and the small plasmid DNA is able to re-nature and dissolve in the solution. Genomic DNA is too large to re-nature its entire length. It and the denatured proteins precipitate out during centrifugation leaving the plasmid DNA in solution.

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