Isolate your own DNA

In textbooks, DNA is usually represented as a twisted molecule and its structure is compared to a twisted rope ladder. The sides of this "rope ladder" are made of sugar and phosphate, the rungs are the four bases adenine, cytosine, guanine and thymine, which are also used for coding. Of course, this structure cannot be seen with a light microscope or even with the naked eye. The DNA molecules are extremely long, but still very small. In order to see what DNA looks like, we need not just one molecule, but a large number of them that cluster together and thus become visible. Therefore, the first question that arises is where DNA is found in the body.

This is where the DNA is located in the body

The complete DNA, which carries the code for the structure of the entire organism, occurs in (almost) all body cells. It is also available in two versions for humans and animals, namely a version inherited from the mother and a version inherited from the father.

• For reasons of stability and space, the DNA, which would be about two meters long in total, is divided into smaller fragments. These are called chromosomes. Humans have 23 different chromosomes, i.e. fragments of DNA. Because of the double set of DNA, there are 46 chromosomes in (almost) every human cell. The opossum has a simple set of 18 chromosomes, that of the horse has 32 chromosomes. The number of chromosomes is often very different from animal species to animal species.
• Plants, as well as some fish or amphibian species, are special in terms of their chromosome set. There may be four or even six to twelve sets of chromosomes.
• The DNA is located in the cell nucleus. For this reason there are cells without DNA when they do not have a nucleus.


Packaging states of the DNA

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• Cells that do not contain DNA in humans and many animal species are, for example, the red blood cells, because these have lost their cell nucleus. It is only still present in this type of cell in birds and reptiles. The white blood cells, on the other hand, still have their nucleus and thus contain DNA.

 How to make DNA visible

First of all, you need to decide which DNA you want to extract. If it is your own, a saliva sample is recommended. How you can best find this out is explained below. Alternatively, you can use a strawberry or a piece of kiwi. Buy the fruit untreated (not cooked, pickled or otherwise treated). The experiment works best with soft, very ripe fruits.

1. Have all the utensils you will need ready. Put the alcohol in the freezer. It should be freezing cold for the experiment. For example, you can use very strong rum, heather spirit or the like, or you can buy pure alcohol in the pharmacy. The alcohol should be as strong as possible and at least 80 percent. If 50 to 70 percent alcohol is used, it is a matter of luck whether the experiment works, and even if it does, it takes significantly longer for the DNA to become visible. Warning: Do not freeze the alcohol, otherwise the bottle could burst.
2. Turn the tap on hot and wait until the water is really hot. Fill a normal drinking glass a quarter full with hot water.
3. Once you've decided to extract DNA from your saliva, take a teaspoon and use it to scrape the saliva off your inner cheekbones. The scraping should be vigorous but not painful in order to preserve as many cells as possible. Transfer the saliva to the hot water and repeat the procedure several times in different places in your mouth.
4. If you prefer to use fruit instead of saliva, cut one or two strawberries or half a kiwi into as small pieces as possible and add them to the hot water.
5. Add a good shot of washing-up liquid (about a tablespoon full) and a teaspoon of meat tenderizer.
6. Now stir the mixture well with a teaspoon. If you use fruit, crush the remaining pieces of fruit on the wall of the vessel. Avoid using a blender, as this can damage the DNA and your future yield would be smaller.
7. Then add half a teaspoon of salt and continue stirring vigorously for five minutes.
8. Place the two coffee filters inside each other to achieve a double filter effect and place them in a clean glass. Pour in your mixture and filter it. You can gently press on the filter to force the liquid through. However, this should be done carefully so that one or both of the filters does not tear. You can throw away the remains in the filter, because the DNA is in the filtered liquid.
9. Now take the alcohol out of the freezer and very carefully pour it into your DNA mixture. You should let it slowly run down the inside of the glass. The alcohol forms its own layer on the DNA mixture. The amount of alcohol added should be (at least) as large as the amount of DNA mixture in the glass.
10. If you now look at the glass, you will notice that white streaks are forming in the middle of the liquid, at the transition between the layer with the mixture and the alcohol layer. This is the DNA that gradually forms flakes.
11. You can now fish out the DNA with a fork or a wooden stick. It will ball itself up in a small, white ball.

This makes it possible to make the DNA visible, because the ball consists of an extremely large number of DNA molecules that have clustered together and thus become large enough to be seen.