Your DNA makes you, you — but how does it work? These talks explore what we know about the genome, the unique genetic sequence that makes up life as we know it.
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What exciting things can you do in this experiment?
In order that you do not only have to imagine DNA in your mind, you will try to make it visible. So visible that you might even be able to touch it. And all this with items that you already have at home or can easily find!
Since not only humans and animals, but also plants and fungi as well as fruits and vegetables contain DNA, we will use a banana for the experiment. Did you know that human DNA resembles the DNA of a banana by about 50%?
Let's go - have fun exploring!
You want to learn more about the code of life?
What exactly happens in each step of this experiment?
How exactly do we get the DNA out of the banana?
How does the genetic code work and what does the taste of coriander have to do with it?
If you want to learn more about DNA and genes, click here!
Overview
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Suitable for age group: 8-14 years
(fascinating for all ages) -
Especially interesting for: Students from grade 7 on, who already have some knowledge about DNA, will well understand the theoretical background of the experiment. But also children who are not yet familiar with the construct of DNA will have fun and gain knowledge.
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Duration: about 30 min
Material
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You most likely already have:
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A teaspoon
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A tablespoon
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Kitchen roll
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Salt
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Dish soap
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A glass
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Hand sanitizer
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You also need:
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A banana
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A plastic bag with seal (freezer bag)
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A funnel (not absolutely necessary, but very helpful)
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A test tube or a small, narrow glass
(it is important that it is transparent) well suited is for example a shot glass or a high drinking glass
Step 1: Preparation
First, get all the materials ready on your table. If you have a freezer bag with a seal, open it and put it aside.
Step 2: Mash Banana
Let's get started! First peel the banana and chop off a 3-4 cm piece (a little less than half the banana).
Put the banana piece in your freezer bag.
Then add the following ingredients to it:
- 1 teaspoon of salt
- 1 tablespoon of dish soap
- approx. 20 mL water
Close the freezer bag and mash the contents with your fingers.
Step 3: Prepare filter
Since we only need the liquid and not the big pieces, we now build a filter. Take a piece of kitchen roll and fold it so that it fits into the funnel. Afterwards you put the funnel on top of an empty glass.
Step 4: Filter
Hold the freezer bag so that there is no liquid in the right corner. Now cut off the lower right corner of the freezer bag.
Watch out!
Be careful that you don't spill anything. When it all works out, you will see a small opening. Through this opening you can now pour your contents into the funnel and collect the liquid (the so-called banana filtrate) in a fresh glass.
Step 5: Layers
The liquid is now filled into a test tube or other glass.
Make sure that the glass is filled up to half of its capacity.
Now take the hand disinfectant and let it run in carefully at the edge of the glass. In the end we want to have as much disinfectant as banana filtrate in the glass.
Step 6: Observe
You should now see 2 layers in your glass.
- The bottom layer (layer 1) is your banana filtrate (which contains the DNA)
- The upper layer (layer 2) is the disinfectant.
Now wait a few minutes until another small layer forms between layer 1 and layer 2. In this layer you can already see the DNA threads. How many minutes does your DNA need until it appears?
After a few minutes your result can look like this. With a little luck, the DNA can be fished out of the glass very easily with a spatula, toothpick or a thin pencil.
Enjoy
experimenting!
In our experiment we ended up with a slimy white substance - DNA. But what exactly happened there? Why do we need the individual steps and ingredients?
Here we explain it to you!
If you have mastered the experiment with the banana well, then you can also try other materials. Try it with mushrooms, a tangerine or a tomato. The important thing is that you always try to "break open" the cell walls by squashing the fruit or vegetable with the other "ingredients".
What happens in each step?
Why do we mash the banana?
In order to get to the DNA in the cell, the cell wall must first be destroyed. We do this mechanically. You can imagine the cell as a balloon with a marble inside. To get to the marble, you have to "burst" the balloon and break it. You can jump on it, or try it with a pencil. Similar, but a bit more complicated is the cell and its DNA.
Why do we add dish soap?
Dish detergent contains surfactants (substances that act as solubilizers) that dissolve the cell membrane and nuclear membrane. This leads to the release of DNA.
Why do we add salt?
Salt increases the solubility of the DNA during the experiment and buffers the pH value.
What happens during filtration?
The following filtration through the kitchen towel separates the coarse cell fragments from the DNA and other dissolved components remaining in the solution.
What happens after adding the hand disinfectant?
Disinfectant consists to a large extent of alcohols. It destabilizes DNA by removing its hydrate envelope.
The hydrate shell is normally located around the phosphate residues of the DNA and consists of water. The alcohol breaks this shell and makes the DNA visible. This process is called "precipitation" in the technical language. When mixed with alcohol, gas bubbles are formed which pull the precipitated DNA threads (which are not surrounded by the water envelope) upwards. Since the DNA is a long thread-like molecule, fibrous precipitates are formed.
Related Links
Created by our Lab Pilots Kim Schmitz, Nellie Prinz, Annabel Mechela and Cécile Hauser
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