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Extraction Process for DNA Analysis

DNA, an acid that holds the cellular design scheme for a living organism, can indicate the presence of an individual at a crime scene, identify a corpse, determine paternity, or simply help researchers learn more about plants and animals. To study the DNA from a specific organism, the researcher must extract it from that organism's tissues. A few basic steps can liberate the DNA from a cell and make it visible for analysis.

  1. Cell Lysis

    • Lysis, the first step in the extraction process, involves breaking cell walls to get to the proteins inside. Common methods of disrupting the cells include freezing, liquifying, use of high-frequency sound, and grinding by hand or with mechanical blades. While all of these methods can open cells successfully, some of them also create heat, which can spoil the proteins, making it necessary to keep specimens and tools chilled.

    Lipid Removal

    • Once the cell membrane has ruptured, detergent can enter the cell and separate lipids (fats) from proteins. Detergents can make non-soluble substances bind with water. Certain detergents known as denaturing detergents disrupt proteins, while non-denaturing detergents will retain the protein structure so the protein can be extracted intact.

    Protein Removal

    • The amino acids within the protein bind to DNA, so the extractor uses an enzyme called protease to release the DNA. Protease breaks protein down by loosening the bonds between amino acids. As an essential part of the digestive process, this action makes it possible for the body to use protein from food. In the laboratory, it allows the extractor to isolate pure DNA from the protein extract.

    DNA Precipitate

    • To make the isolated DNA visible, the extractor creates a precipitate, a solid derived from a liquid solution. The liquid sample is submerged in a mixture of cold ethanol, a type of alcohol, and salt. Since DNA does not mix with alcohol, the DNA sample forms a wispy white mass within the stirred solution, making it easy to see with the naked eye. The salt helps prevent any of the DNA from remaining dissolved in the water from the original sample.

    Analysis

    • DNA can answer many questions under analysis. Each of us carries a unique genetic "fingerprint" in our DNA, and experts need only a tiny tissue sample to match the DNA to a specific person. This technique, called DNA profiling, can help determine a biological relationship between people, confirm a suspect's presence at the scene of a crime, or reveal the migration patterns of humankind throughout history. DNA studies also shed light on genetic diseases and their possible cures.

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