DNA extraction/isolation is the purification of DNA using combination of various methods. DNA Extraction is a significant procedure in molecular biological methods and in forensic analysis. Several different extraction kits and protocols/methods are available.
Proper extraction methods and procedures should be chosen to get the process optimized and also to save time. The goal of DNA extraction process is to produce high quality DNA and to remove inhibitors that inhibit the polymerase chain reaction. DNA samples are most susceptible to contamination during the extraction process. Laboratories usually process the evidence DNA samples at different locations and times.
Basic procedures for DNA extraction are as follows
- Break the cells open to expose DNA along with the cytoplasm.
- Removing membrane lipids by adding a detergent.
- Remove proteins by adding protease.
- The solution is then treated with saline to clump the debris (RNA, lipids, proteins) together.
- Centrifugation is performed to separate DNA from the debris.
- DNA purification is performed using ethanol.
- Isolate DNA and solubilize in Tris EDTA (TE) or ultrapure water. DNA is more stable in Tris EDTA
DNA is stored at -20C or -80C for long term storage in order to prevent the action of Nucleases. Nucleases degrade the DNA. Nucleases need magnesium to work, so one of the way to prevent nucleases from digesting DNA in the blood is by using purple topped tubes that contain EDTA. EDTA is a blood preservative and a chelating agent. It binds with most of the magnesium in the tube and prevents DNA from degradation.