While DNA extraction methods have been around for over 150 years, ever since Friedrich Miescher isolated it for the first time in 1869, countless iterations of DNA extraction protocols have occurred since then. Different lab extraction systems are used depending on the type of cell, how the cells have been preserved (e.g., in formalin versus freshly harvested from living tissue), and the purpose of extracting the DNA.
DNA Extraction Protocols
Despite the seemingly endless variants to DNA extraction methods, in reality, all methods use three basic steps in every lab extraction system. Regardless of the specifics, each method requires that you:
- First break the integrity of the cell membrane in animal cells or the cell wall in plant cells and most bacteria. This is done with enzymes, chemicals, or mechanical disruption.
- Next, once the outer cellular membrane is disrupted, the second step requires you to lyse the nuclear membrane inside of which is the DNA. To do this, you can use enzymes or chemicals.
- In the third and final step, various separation techniques are used to separate the various components of your cells, including the sought-after DNA.
The Two Primary DNA Extraction Methods
Regardless of which specific method is employed, you will either use a chemical-based or solid-phase DNA extraction technique. In the chemical-based method, organic-based and inorganic-based chemicals are used. Lab extraction systems that use phenol, chloroform, and isoamyl alcohol (PCI) are regarded as the best DNA extraction protocols of all, but due to the harmful nature of the organic chemicals, this method is restricted. The use of automated machines, however, allows you to perform the gold standard of DNA extraction methods (i.e., PCI) safely and rapidly.
Proteinase K and salt are the most popular inorganic chemicals used for DNA extraction. While salt can be used alone to extract DNA, more commonly it is used in combination with proteinase K, Tris, EDTA, and other chemicals.
DNA extraction methods that use a solid-phase protocol have become more popular lately. Very often, silica is used to bind the DNA during the extraction procedure making it easier to isolate the DNA from the rest of the cellular debris.
A relatively new DNA extraction method is the use of magnetic beads that bind the DNA. Wash and extraction buffers are used to clean and ultimately elute the DNA from the magnetic beads. The advantages, however, of this technique includes a lower cost, shorter procedure time, and no need to use dangerous chemicals.
Which DNA Extraction Method is Best?
There is no simple or single answer to this question. The DNA extraction protocol you should choose for your laboratory depends on factors such as the quantity of DNA to be extracted, the purity of the DNA needed, the time and cost of the particular DNA extraction method chosen, and the size of the original sample needed to obtain the necessary final product. One way to ensure consistency, high productivity, and low long-term cost is by using automation whenever possible in your lab extraction systems.
By using automated systems, modern DNA extraction methods have become more efficient, safe, inexpensive, and commonplace in the science and pharmaceutical laboratory. It has even been suggested that in the future, the best scientist will have to know a combination of science expertise and engineering to maximize the use of robotics and laboratory automation.
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