What Is the Purpose of Salt in DNA Extraction?

During the extraction of deoxyribonucleic acid, or DNA, salt compounds such as sodium acetate and ammonium acetate are typically added to aid in the removal of DNA-associated proteins. Another type of salt compound called sodium chloride, or NaCl, helps in solidifying and making DNA visible. When mixed in an alcohol solution, the sodium component of NaCl provides a protective barrier around the negatively-charged DNA phosphate ends, enabling them to move closer to be extracted out of the solution.

DNA extraction is the process of obtaining pure DNA from a sample, either from living or non-living cells, such as those found in viruses. This technique is commonly used in the medical field, where early detection of diseases and disorders significantly increases the survival rates of afflicted individuals.

The method initially requires the lysis of cells that contain the DNA to be extracted. The cells disintegrate by subjecting the sample to ultrasonic oscillations or by bead beating. The sample is added with salt, which is centrifuged in a solution of phenol-chloroform. The associated protein molecules are then drawn out. The DNA that is left after the removal of the proteins is mixed with an alcohol solution, typically cold isopropanol or ethanol. The solution is centrifuged, and DNA, which does not dissolve in alcohol, is precipitated and extracted. To increase DNA yield, the entire process must be performed in a cold environment.