DNA Extraction
From Halbeeg, the open encyclopedia · Af-Soomaali
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DNA extraction is a laboratory technique for isolating DNA (the molecule containing genetic information) from cells and other materials such as proteins, lipids, and RNA. The aim is to obtain pure DNA suitable for subsequent tests.
The technique is used in molecular biology research, medicine (diagnosis of genetic diseases), forensics, paternity identification, and verification of food and plant and animal species. DNA can be extracted from blood, saliva, hair, plant tissue, bacteria, and environmental samples.
Basic steps
Most protocols follow three broad steps. First is cell lysis, which ruptures the cell membrane and nuclear envelope using salt, detergents such as SDS, and enzymes such as proteinase K. Second is removal of contaminants: proteins and lipids are separated or precipitated out. Third is collection and purification of DNA using water or buffer.
Common methods
The phenol–chloroform method uses two liquid phases: proteins move to the organic phase, while DNA remains in the aqueous phase. The DNA is then precipitated by adding ethanol or isopropanol along with salt. Another widely used method employs silica columns: DNA binds to silica in high-salt conditions, contaminants are washed away, and DNA is eluted in a weak buffer. Magnetic bead methods are also available and can be automated.
Quality assessment
After extraction, quality is measured by spectrophotometry. The 260/280 nm ratio indicates whether protein contamination remains, while gel electrophoresis shows whether the DNA is intact and undegraded. If the DNA is heavily contaminated, tests such as PCR may fail.