HOME＞Experiments＞For Kitchen＞EH002 DNA Extraction
Let’s extract DNA from cells. Plant DNA is enclosed within three barriers: the nucleus, cell membrane, and cell wall. We’ll break these barriers physically and chemically to dissolve the DNA. Finally, adding ethanol will cause a white substance to appear!
Ethanol is a highly flammable substance. Make sure to handle it with a guardian and carefully check for any sources of ignition beforehand.
In the field of biochemistry, “ethanol precipitation” is sometimes used as a method to extract DNA from cells. Many of you may have encountered this in school science classes. Broccoli is often used in such lessons, but grinding it in a mortar can be a bit labor-intensive. So, let me introduce an alternative method!
Requires
equipments
・ziplock bag
・glass
・bowl
・drain net
reagents
・Fruits that are easy to mash by hand
・table salt
・dish soap
・ethanol
Preparation
If the fruit has hard parts like cores, peels, or stems, remove them beforehand. Chill the ethanol in the refrigerator in advance.
Methods
1.
In an appropriate container, mix 180 mL of water, 1 tablespoon of salt, and 20 mL of dish soap. Store the mixture in the refrigerator.
2.
Place the fruit in a zipper bag, seal it, and mash the fruit thoroughly with your hands.
3.
Pour the liquid you prepared earlier into the zipper bag and mix it well with the mashed fruit by kneading.
4.
Layer a drain net three times and set it over a bowl. Pour the contents of the zipper bag into the net to filter it. Transfer the filtered liquid into a cup.
5.
Take the ethanol out of the refrigerator and gently pour it into the filtered liquid.
6.
If a white substance (DNA) appears at the top, it is successful.
Clearing
The liquid remaining after the experiment contains ethanol, which poses a fire risk if poured directly down the drain. Absorb the ethanol portion with a rag or unwanted paper, let it dry completely, and then dispose of it as combustible waste. Pour the remaining liquid down the drain and run water from the tap for a while to flush it thoroughly.
Dispose of the leftover fruit along with the drain net as combustible waste.
Principle
Plant cell DNA is enclosed by the cell wall, cell membrane, and the nucleus. To extract the DNA, these barriers need to be broken down in order to release the DNA from the cell.
In the previous experimental procedure, the fruit is first mashed to break the cell wall. Then, by mixing with detergent, the protein-based cell membrane and nuclear membrane are dissolved.
The DNA has been released from the cells, but it is still dispersed in the solution and not visible to the naked eye. It needs to be aggregated to make it visible.
DNA contains negatively charged phosphate groups, which cause the DNA molecules to repel each other like magnets. To counteract this force, salt is added. The Na+ ions from the salt weaken the repulsive forces between the phosphate groups, allowing the DNA molecules to clump together more easily.
Finally, by adding ethanol, the DNA cannot dissolve completely and precipitates at the interface between the ethanol and the solution.