DNA EXTRACTION
DNA is extracted from human cells for a variety of reasons. With a pure sample of DNA you can test a newborn for a genetic disease, body identification, or analyse forensic evidences.
DNA EXTRACTION
DNA extraction is a process of purification of DNA from sample using a combination of physical and chemical methods. The first isolation of DNA was done in 1869 by Friedrich Miescher. Currently, it is a routine procedure in molecular biology or forensic science. DNA extraction is typically the first step in a longer laboratory process. It is an important part of that process because the DNA first needs to be purified away form proteins and other cellular contaminants. DNA is located in cells. Inside almost every cells in our bodies is a nucleus, and inside each nucleus is about two meters of DNA.
There are 4 steps in a process to purify DNA from a cheek swab:
1. Collect cheek cells.
2. Burst cells open to release DNA.
3. Separate DNA from proteins and debris.
4. Isolate concentrated DNA.
Materials:
- Warm water bath
- Micro-centrifuge
- Buccal swap
- Micropippetors
- Sample tubes
- Lysis solution
- Concentrated salt solution
- Resuspension buffer
- Ethanol
- Isopropyl alcohol
Process:
1. Collect cheek cells:
Use the buccal swab to collect a sample (cheek cells) inside the subject's mouth
Next, place the swab into an Eppendorf tube. It is covered with hundred of tiny cheek cells. Inside each cheek cell is a nucleus, and inside the nucleus is the DNA.
1. Collect cheek cells.
2. Burst cells open to release DNA.
3. Separate DNA from proteins and debris.
4. Isolate concentrated DNA.
Materials:
- Warm water bath
- Micro-centrifuge
- Buccal swap
- Micropippetors
- Sample tubes
- Lysis solution
- Concentrated salt solution
- Resuspension buffer
- Ethanol
- Isopropyl alcohol
Process:
1. Collect cheek cells:
Use the buccal swab to collect a sample (cheek cells) inside the subject's mouth
Next, place the swab into an Eppendorf tube. It is covered with hundred of tiny cheek cells. Inside each cheek cell is a nucleus, and inside the nucleus is the DNA.
2. Burst cells open to release DNA:
The end of the swab must be cut off so it will be able to close the tube. Using the micropippetor, add some lysis solution to the tube.
The end of the swab must be cut off so it will be able to close the tube. Using the micropippetor, add some lysis solution to the tube.
Place the tube into the warm water bath.
The lysis solution contains 2 important ingredients: detergent and an enzyme called proteinase K. The detergent disrupts the cell membrane and nuclear envelope, causing the cells to burst open and release their DNA. The proteinase K cuts apart the histones to free the DNA.
3. Separate DNA from proteins and debris:
Once the DNA is freed from the cells and the swab have been removed from the tube, add some concentrated salt solution to the tube.
The salt causes proteins and other cellular debris to clump together.
Place the tube into the centrifuge. Add another tube containing water opposite the main tube to balance the centrifuge. Close the centrifuge and turn it on.
Inside the centrifuge, the tubes around at high speed. The heavy clumps of protein and cellular debris sink to the bottom of the tube, while the strands DNA still remain in the liquid.
Use a micropipettor to remove the top liquid (contains DNA) and place it into a clean tube.
4. Isolate concentrated DNA:
Add some isopropyl alcohol to the tube. Inverting the tubes several times mixes the isopropyl alcohol and the liquid contains DNA. Because DNA is not soluble in isopropyl alcohol, it comes out of solution. From now, the clumped DNA can be seen with your naked eye.
Place the tube into the centrifuge and turn it on. This time, after the sample spins in the centrifuge, the DNA sinks to the bottom of the tube. Once the liquid is removed and the DNA is allowed to dry, you can use it for many further purposes or you can store it in the freezer for many years.