DNA is the basis of life on earth: every living being has DNA. Police officers use DNA traces to solve crimes. But it's not that easy to understand what DNA actually is. Usually we cannot see it.
Here we show you how you can isolate DNA from a banana at home and make it visible, and you will learn even more about this topic.
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!
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!
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.
Duration: about 30 min
You most likely already have:
You also need:
A plastic bag with seal (freezer bag)
A funnel (not absolutely necessary, but very helpful)
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:
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.
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.
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.
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".
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.
Dish detergent contains surfactants (substances that act as solubilizers) that dissolve the cell membrane and nuclear membrane. This leads to the release of DNA.
Salt increases the solubility of the DNA during the experiment and buffers the pH value.
The following filtration through the kitchen towel separates the coarse cell fragments from the DNA and other dissolved components remaining in the solution.
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.
What is DNA? This video designed for kids is a fun/exciting way to introduce DNA to children. In this video kids will learn facts all about DNA, what it is made of, chromosomes, traits and much more.
© Clarendon Learning
In this video by wehi.tv for Science-Art exhibition you can see high quality animations of DNA transcription, translation and other things that are going on inside of your cells.
It is true that specific genes are associated with the perception of certain tastes, or to be more precise smells, because nearly all of what we think of as taste is really volatile chemicals being detected in our nose.
© New Scientist
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