The most common method for the extraction of DNA fragments from gels is the spin column method. The agarose gel is used to run DNA samples and elute bound DNA. The DNA is then cleaned with a solvent such as butanol. Once the DNA has been clean, it can be sent to a microfuge tube for amplification. However, for the best results, the agarose gel should be used only once.
The first step in the DNA extraction process is to prepare agarose gel for electrophoresis. The DNA fragments are separated on the gel using a gel electrophoresis procedure. After this, the desired DNA fragments are selected against a molecular weight standard and visualized against ultraviolet light. Then, the desired DNA fragment is excised from the gel. Commercial kits are available on the market that make this process easy. These kits contain silica-type membrane spin columns, buffers, and wash solutions.
The next step is to prepare the sample. The agarose gel must be cleaned thoroughly. Using an alcohol-based wash is not recommended because the solution contains a high level of ethidium bromide residue. The gel piece is then placed in a 500-ul centrifuge tube. The solution in the Eppendorf tube should be saved for future use. Depending on the agarose gel piece, the volume recovered is usually fifteen to thirty ul. Aim to recover between 30 to sixty percent of the DNA fragments from the gel.
The next step is to place the DNA fragment in a dialysis tube. The tubing is impermeable to DNA molecules, so the DNA molecules are trapped in the tube. The electric field around the tubing is long enough to separate the DNA from the gel. Then, the solution can be pipetted out to obtain the desired DNA. These steps can be repeated as many times as necessary.
This method involves placing the fragmented gel into a dialysis tube that is impermeable to DNA molecules. After this, an electric field is established around the tubing. This electric field allows the DNA fragments to be removed from the gel. The next step is to pipett the solution to the desired DNA. Once the sample is ready, the remaining agarose is stored in the gel.
The agarose gel was placed on a cushion filter. A 1.7-ml Eppendorf tube was then put into the centrifuge. The DNA fragments were centrifuged at 5,000 to 10,000 rpm for 5 minutes to recover DNA fragments of the desired size. The process is very simple and does not require any specialized equipment. The technique can be applied to any type of gel, including the DNA.