Extracting Information: DNA Extraction and Purification

Charles Becker became proficient at DNA extraction and purification. In our laboratory, researchers use fresh or frozen whole blood samples from which to extract DNA necessary for our ongoing genetic research.

Researchers can extract and purify DNA in one of two ways, using either the precipitation method or the column-based method. The precipitation method requires both intact white blood cells (only white blood cells contain DNA) and non-degraded DNA and is used primarily for smaller sample sizes. In contrast, the column-based method only requires non-degraded DNA and is more efficient for larger sample sizes (96 or greater), and is the method most often used in our laboratory.

Both methods require researchers to separate the blood cells (red blood cells, white blood cells, and plasma) via centrifuge; however, the precipitation method requires researchers to precipitate a pellet of DNA from the protein contained within intact white blood cells.

With column-based extraction, researchers first add a protease—an enzyme or substance that breaks down protein into peptides—to each blood sample. In a series of steps, researchers separate the cells until only the DNA remains. A silica gel membrane lining the bottom of each column causes DNA to "stick to" the surface of the membrane after researchers have cleansed it of amino acids and salts.

Using a very large number of samples, Becker successfully completed the process of DNA extraction and purification using one or the other of these two methods.

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