5 biological experiments to do at home

1. Homemade extraction of your own DNA

Ingredients: transparent glass, salt, liquid soap, grapefruit juice, and alcohol (e.g. disinfectant, rum, vodka, etc.).

The first step consists of spitting on the glass and adding a pinch of salt to it. Then, add some liquid soap (like the one you use for washing the dishes), juice from a grapefruit, and some drops of alcohol. Once you have everything on the glass, stir the mixture, et voilà.

The white mucous filaments you observe on top of the mixture is your DNA. See more on how right here.

The saliva contains cells from your mouth that have DNA inside them. The detergent is used to break down the membranes that protect the DNA, and releases it into the recipient. The salt makes the DNA denature* and precipitate, while the grapefruit juice neutralizes the proteins that could damage the DNA.

2. Cultivate the bacteria that grow on your hand

Ingredients: small airtight container, gelatin dessert

If you buy gelatin from a package, follow the instructions to make it. If you do not find gelatin to make, it should be even easier and just touch the gelatin from the glass jar and wait to see what happens.

Check out what gelatin solution looks like

Heat water on the stove and add the package contents to it, stirring the mixture vigorously until the gelatin grains dissolve. While the solution is still hot, pour into container where you want to cultivate your bacteria, and put the lid on in order to avoid contamination. Store the container in the fridge overnight so the gelatin can solidify. Remove from fridge once solid, touch the gelatin, put the lid on again and leave the container at room temp or near the radiator for a few days.

After some days you will see some white spots on the gelatin. These are your hands’ skin bacteria. Even if you try to wash your hands and repeat the experiment again, we will always have bacteria on our hands.

Microorganisms are everywhere but we do not normally see them since they are so tiny and dispersed. In this case, they use the gelatin as food, and since there are so many nutrients in it they can divide (reproduce) many times and accumulate in the container until we are actually able to see them.

3. Change the color of your flowers

Ingredients: flowers (preferably with white petals), ink, a glass, and water

One of the easiest experiments you can do. Place the flower in a glass with water and colored ink (red, black, blue, etc.). After a while you will see the petals have colored petal ribs or veins, of the same color of the ink you added to the water.

Are you flowers dying out? Why not give them some color?

Normally we give water to plants in order to keep them alive. Plants have a tube system (called xylem) that distributes water and some nutrients to all parts of the plant. Using the colored water we are actually able to see this tube system.

4. Egg ball

Ingredients: eggs, vinegar, and a pot with lid (really important, as this keeps the smell inside!)

Place the egg (including shell) into the pot with vinegar and cover it with the lid. Let it sit for some days. After this, you will have a flexible smelly egg that you can use as a ball.

The single cell present in one egg, due to its importance in reproduction, is protected by an eggshell. This shell is made of calcium carbonate that reacts with the acetic acid present in the vinegar, causing its decomposition, and leading to a ‘naked’ egg that has increased flexibility.

Interested in chemical experiments? There is a set here.

5. Cook an egg with no heat

Ingredients: eggs, bowl, alcohol

Want to innovate your cooking skills? Next time you want to cook an egg , place it into a bowl and add some alcohol to it. After some minutes you can see how it slowly ‘cooks’. Unfortunately, I cannot guarantee that you will find it extremely delicious.

Cooking an egg, consists simply on denaturing* the proteins that are present in the cell contained by the eggshell. This protein denaturation is normally obtained by heat exposure (boiling or frying), but another way consists of adding compounds such as alcohol that denature the proteins by interacting with them and altering their 3D structure.

denaturation*= process by which a biomolecule (e.g. DNA, protein), losses its 3D structure.

You can see my original article here:


Can you get ice colder than 0 celsius degrees?

The answer is YES!

If you take water and freeze it in the freezer, it will turn into ice and have a temperature around 0C. But if you then add acetone, the temperature can go DOWN to -15C.

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Why does the acetone make ice colder?

This is because it is an endothermic reaction, so instead of releasing more heat (such as for example burning wood or carbon), it will take heat, and therefore the ice becomes colder.

Why not cultivate the bacteria and fungi that are growing on your mobile?

Why not cultivate the bacteria and fungi that are growing on your mobile?

On a previous post I described how you can cultivate the bacteria that grow on your hand, in order to obtain your “own  bacterial print”.

Recently I just saw this article about finding out which bacteria are normally present on on the surface of your mobile phone.

You see bacteria are everywhere so don’t get scared, but are you brave enough to find out to which kind of bacteria are you exposed everyday?

How to prepare a homemade culture medium:

Bacteria are the most used organisms for studying the proteome and the genome. Once, understood on this organisms ( since they are easy to grow up, relatively cheap and they multiply rapidly), thanks to informatics tools it is possible to encounter the human homologous ( since the human genome has been already sequenced).

The most used growing medium for bacteria is agar-agar. This one comes from red algae ( Phylum Rodophyta), for e.g. the ones that belong to the next genders: Gelidium, Euchema, Gracilaria.

In order to obtain the agar-agar, you have to identify the algae, previously mentioned; recollect them and boil them. Once they have been submitted to this process, a gelatinous, transparent liquid will appear, which is agar. This will happen even though for the ones that don’t have the sea close, so they can made it , there are two other options left:

The first one is to buy it on a naturist shop (in Spain is around 20 € for 100 g).

The second option that I “personally developed” is the gelatin. This is a medium that contains all the nutrients necessary for the normal bacterial development      (further on a mention about the selective mediums will be made) and it is cheaper. Even though there is a small inconvenient: the bacteria got buried on the medium (because they consume it) and as the time passes by the bacterial manipulation get worse. This is why I recommend to select the interest bacterial colony and to grow it on a new plate after one week as much.

You simply have to follow the instructions that are written on the package:

  1. Heat water on a recipient.
  2. Add the package content to the recipient and stir the mixture vigorously until the solute (the gelatin grains) stops being observed anymore and the dissolution becomes homogenous.
  3. When the dissolution is still hot, it has to be poured on the recipients where the bacteria will be grown (so many recipients as necessary for the experiment, but not forgetting the control plat, where no microorganisms are expected to grow).
  4. Once the plate is ready, they have to be hermetically closed (in this way a possible contamination is avoided), and placed on the fridge overnight, so the gelatin can solidify.

Some typical examples to understand the microbial populations are: to touch the plate that you introduced on the fridge (it will appear the microbiota present on the cutaneous surface), to spread a small sample of liquid from a lake, river or puddle or by taking a sample of the ground and mix it with water, so you can spread it over the plate and observe this way the different phenotype of the bacterial colonies.



Bacterial growth of cutaneous microbiota. Day 3.


Control plate. Day 3.

I hope that you find this post interesting, helpful and if you have any difficulties, suggestions or critics, don’t doubt to send a commentary.

P.S. Apologize for my English but I think that it is better at least than the Google Translator.