DNA Extraction

Basically, a nucleic acid, the DNA provides genetic information necessary for the development of living beings. The DNA is analogous to the blueprint used in designing a building. It is composed of polymers strands, that are aligned parallel to each other. The phosphates and sugars which form the bulk of these polymer strands are linked by ester bonds. The DNA stores information encoded in segments known as 'genes'.

Process of DNA Extraction

DNA can be extracted from a variety of cells including blood cells. In the DNA extraction process, the cells are broken to obtain the DNA. The breaking of a cell is also known as 'cell lysis' or 'cell disruption'. It is done by a technique known as sonication. During sonication, the particles present inside the cell are disrupted and their alignment is broken with the help of sound energy. After cell lysis, the lipids present in the cells are removed by the means of a detergent. The next step in the process of DNA extraction is to remove the proteins. Protease is added to remove the proteins. Finally, the DNA is 'precipitated' using an alcohol. Precipitation is the process of segregating solid particles from a solution. The alcohols that are commonly used in the precipitation process are isopropanol or ice-cold ethanol. To precipitate the DNA, centrifugation of the solution containing DNA is carried out. It not only separates the DNA, but also removes salts from the solution.

DNA Extraction by Anion-exchange Method: This method uses the chromatography technique for extracting DNA from cells. The nucleic acids present in the DNA are composed of phosphates. The phosphates hold a negative charge. In the anion-exchange method, a positively charged substrate is used to bind the phosphates that are negatively charged. Cellular proteins, RNA (Ribonucleic acid) and metabolites are removed with the help of medium-salt buffers.

DNA Extraction Using Silica Gel: The advantage of using this technique is that, the method is fast, reliable and economical. This method uses a silica-gel membrane to adsorb the nucleic acids of DNA. Chaotropic salts used in the process act as catalysts. The buffers used in the lysis of the cells are optimum in quantity. This helps in the adsorption of DNA on the silica-gel membrane, while the metabolites and proteins are washed away.

The extracted DNA is visible to the naked eye after it is centrifuged. Centrifugation is the process in which the solid particles from the solution are separated with the help of mechanical force. It is done by means of a centrifuge machine. The DNA extract formed after the process gets deposited in the form of pellets. It can also be used in DNA fingerprinting. Thus, DNA extraction and isolation is necessary for us to understand its importance in forensic science and research.

Beginners or students experimenting in DNA extraction use plants such as peas, onion and wheat. The DNA extraction process or 'experiment' has also been introduced into school curriculum to facilitate a better understanding of DNA and genes among students. Conducting the experiment of DNA extraction in schools helps the students in understanding various concepts related to the DNA. It helps them to study the principles of inheritance, biotechnology, etc.