What is common across all living things?
All living things are capable of movement – whether it’s something we can see or movement at the microscopic level.
All living things also produce energy from food that they take or create, a process known as cellular respiration.
All living things can reproduce, and some living things do this independently through a process called asexual reproduction, or with a partner through a process called sexual reproduction.
All living things can grow and develop – and this involves growing in size, or changing our physical characteristics dependent on our needs and the environment we are in.
All living things can achieve a state of balance, where we can change the number and types of chemicals inside our cells to be in harmony with our surroundings.
All living things react to our environment. We shiver when it’s cold, and we sweat when it’s hot. Plants move towards the sun, and animals run from predators. All living things can sense the environment and react to survive.
All living things are capable of adaptation. We can change our behavior and growth patterns to make the most of the resources available to us.
But what is common across all these common things? For living things to be able to have all seven of the characteristics above, they must follow a precise set of instructions found within all living cells. This set of instructions is probably one of the oldest languages ever created, and it is understood by all living things at the cellular level – meaning, whether the organism is a bacterium or a complex animal, their cells are speaking the same language. This language is written in the form of DNA.
DNA stands for deoxyribonucleic acid. It is a unique molecule that has phosphates, sugars, and nitrogen-rich groups. It is made up of four building blocks called adenine (A), thymine (T), guanine (G), and cytosine (C). And with the unique sequences made of these four building blocks, the DNA provides instructions for all living things to move, produce energy, reproduce, grow, be balanced, react to the environment, and adapt.
So, it is not surprising that scientists have been working long and hard to fully understand DNA. One of the initial steps to study DNA is to extract it from inside the cells of living things. Normally, this process is done in the lab, in very clean and controlled environments to prevent contamination and to prevent damage to the DNA.
But did you know that you can practice extracting DNA at home? This module will show you how.
What You Need
50 g of any type of fruit, vegetable, or raw meat
1 tablespoon of rock salt or iodized salt
1 tablespoon of pineapple juice, lemon juice, or contact lens solution
1 cup of cold water
1 tablespoon of detergent, shampoo, or liquid soap
1 cup of cold 70% ethyl alcohol
Blender
Knife
Chopping board
What You Do:
Chop the fruit, vegetable, or raw meat into small pieces.
Mix 1 tablespoon of salt with 1 cup of cold water. Stir until fully dissolved.
Add the chopped fruit/vegetable/meat to the saltwater solution and transfer to a blender. Grind/liquefy for 30 seconds.
Note: If a blender is unavailable, transfer the chopped fruit/vegetable/meat into a ziplock bag and pulverize the material until it is turned into mush.
Each of the components of this experiment has a unique purpose:
50 g of any type of fruit, vegetable, or raw meat
These serve as the sources of DNA. They contain cells with DNA inside them. The DNA is found within structures that are called:
Nucleus – the portion of the cell where most of the DNA is found. This is where most of the DNA stays to provide instructions to the cells.
Mitochondria – the portion of the cell responsible for providing energy. It also keeps small amounts of DNA to direct the process of energy creation.
Chloroplast – a structure unique to plants, this portion is the one that captures sunlight to create sugars in a process called photosynthesis. These sugars serve as energy sources for plants and the animals that eat them. The chloroplast also has small amounts of DNA to direct the process of photosynthesis.
1 tablespoon of rock salt or iodized salt
The iodized salt creates an environment where the DNA is stable outside of the cell. As a molecule, the DNA is negatively charged and so having ions like those in salt (sodium ions and chloride ions) can help it remain stable.
1 tablespoon of pineapple juice, lemon juice, or contact lens solution
These substances are acidic and contain chemicals that can break down protein. By adding these, we weaken the structure of the cells of the fruit, vegetable, or raw meat so they can release the DNA.
1 cup of cold water
Our cells are made up of 70% water. By adding water to the solution, we are mimicking the environment of the cell. We must keep it cold to make sure that the DNA is preserved and does not break down because of heat.
1 tablespoon of detergent, shampoo, or liquid soap
The detergent, shampoo, or liquid soap completely removes the portion of the cells that keep or contain the DNA. Our cells are closed to the environment through a structure called the cell membrane. The cell membrane is made up of chemicals called lipids – which are very similar to the fats and oils we find in our food. Whenever we wash the dishes with soap or whenever we wash our hair with shampoo, they remove the oils in the dishes and our hair. By adding these to our mixture, we also remove the lipids in the cell membrane that frees the DNA completely.
1 cup of cold 70% ethyl alcohol
Ethyl alcohol, or ethanol, is a unique liquid that interacts differently with DNA. Instead of dissolving DNA, it makes it turn into a visible solid called a precipitate. So, by adding alcohol, we make DNA visible. This is also cold to make sure that DNA is not destroyed by heat.
Blender and Knife
They help us break down the complex structures of the tissues and cells in the fruit, vegetable, or raw meat that we will be using. This makes it easier for us to reach the cells and open them up to release the DNA.
Different types of cells have different amounts of DNA. You can experiment with this experiment by trying to extract DNA from different types of fruits and vegetables to see which will produce more DNA!
Once scientists have extracted the DNA, we do more analysis in the lab to determine the sequences found within them. They can tell us different types of information, such as:
The identity of the organism (what species it is)
How it evolved and to which organisms it is more closely related to
If it has mutations that can make it stronger or weaker
And so much more!
It is amazing how the DNA connects all living things – great and small – in the world! It shows us how we must treat all living things with respect, and that we are all equally responsible for taking care of the planet.