“Learn how to extract DNA from strawberries at home using simple household items. A fun and easy science experiment for all ages!“
I’m a geneticist, I work with DNA every single day. It is our job to uncover the secret of life’s tiniest molecule.
Whether we are doing a DNA test, forensic, diagnosis or simply research, DNA is always at the centre of my world. But how exactly do we get the DNA and do experiments? That’s what I will teach you in this article.
I’m explaining to you- DNA extraction, a fundamental genetic process.
The objective of writing the present article is to introduce DNA extraction to students from the very beginning and how to perform it using household things. In addition, teachers and educators also gain insight into the basics.
Stay tuned.
Key Topics:
What is DNA?
We explained DNA many times on our blog. I will give links to those articles, but this article is very beginner-friendly, so I try hard to make it as simple as possible.
Related article: Unraveling the Mystery of DNA: Definition, Structure, Function and Types.
Our body is made up of cells. Cells have cellular organelles, a nucleus and the cell wall or membrane- the outer cover of the cell! You know it! Right?
Now, DNA is present in the cell nucleus, which is why the name ribonucleic acid has been given. And, it’s acidic.
Our DNA works like a computer. What does a computer do? It stores, expresses and transfers the information, right! For instance, it stores our picture, shows us when we click on it (expresses) and we can also transfer it from one computer to another or to a phone.
Similarly, our DNA stores, expresses and transfers genetic information from one generation to another. Our cellular DNA has all the information to survive, reproduce and develop on Earth!
Not only for us, but for all living beings.
Now you know why DNA is so crucial for us! Studying DNA will help us gain insight into our genetic information. Thereby, any health-related issues associated with a person can be investigated. However, we need to extract DNA first.
What is DNA extraction?
Imagine a circle of students, then another circle inside and the teacher in the centre. You are one of the students. You have to help your teacher escape. What do you have to do?
First, you need to break the first circle, then another. Is it? We have to do the same here. The first student circle is our cell envelope, the second circle (inside) is our nucleus and the teacher is our DNA.
To obtain the DNA, your teacher! You need to break the cell layer: the cell wall or membrane and the nuclear envelope.
That’s DNA extraction!
“The combination of physical and chemical treatment for cell wall and nuclear membrane lysis is known as DNA extraction.”
How to Extract the DNA?
We need to follow a few steps for DNA extraction.
- Tissue lysate is prepared by physical treatment, for instance, grinding the tissue using a mortar and pestle or tapping. It’s used particularly for plant tissues. This physically breaks the cellular structure, particularly the cell wall.
- The tissue crude is treated using the lysis buffer and breaks the cell wall and nuclear envelope. Lysis buffer contains chemicals that help in lysis.
- Now we have a thick and slurry-type lysate, centrifuge it or put it aside for some time to collect the liquid part. This liquid contains our DNA.
- After collecting the liquid, add pre-chilled alcohol (isopropanol or ethanol) to precipitate the DNA.
- Now, our DNA is extracted! We need to dissolve it in the buffer or water.
I am teaching you the actual/practical process of DNA extraction, but unfortunately, your school lab doesn’t have any of these chemicals or instruments. I know it, certainly!
So, how can we do that?
Don’t worry, we will learn DNA extraction only using several household things and 2 pieces of tasty and juicy strawberries.
You are thinking– why strawberries, not apples or dragon fruit? We need to address this first.
Why are strawberries used for DNA extraction?
Strawberry is juicy, tangy + sweet, and is everyone’s favorite. Therefore, used in DNA extraction. Just kidding!
I am giving you five scientific reasons behind that.
Cultivated strawberry, which we are eating, has been developed through the hybridization between two different native strawberry species (Fragaria x ananassa). It is octoploid– meaning it has 8 different chromosome copies.
It has 7 chromosomes, each with 8 copies, so the total number of chromosomes in its genome is 56. We humans have 46 chromosomes in 23 pairs (diploid). The higher copy number increases the DNA yield.
Meaning that there is a high chance, we get the DNA.
Second, the mature strawberry fruit is filled with a huge amount of water and sugar, helping break the cell wall components like pectin, cellulose and polysaccharides.
By the way, this makes the fruit juicy, sweet and delicious.
In addition, the water intact increases the size of cells, relative and helps to break open the cells and extract the DNA.
Strawberry has enzymes like pectinase and cellulase, which degrade its outer cell coat that contains pectin and cellulose. Note that the plant cell wall is rich in pectin, cellulose and polysaccharides.
It can easily be mashed due to its soft, fleshy and watery nature. This helps to prepare an amazing lysate for DNA extraction.
Imagine you want to make the pest of plant leaves and fruit (strawberry), which prepares a good and consistent slurry? The fruit, am I right?
Lastly, its cells have high water content, which again helps to prepare a good cell lysate and helps during the cell lysis process.
In conclusion, the high water content, presence or unique enzymes (pectinase and cellulase), an octoploid genome and larger cell size are a few reasons strawberries are the best tissues to demonstrate DNA extraction.
How to extract DNA from strawberries?
We only need four household items to extract the DNA from strawberries. Any wash agent (washing powder or dishwasher), salt, water and spirit or alcohol (lab grade). That’s it. We also need a filter paper, any plastic straw, a beaker or a test tube.
To get good results, we need to use alcohol like ethanol or isopropanol, but for demonstration purposes, we can use the spirit. I will show you by actual experimentation.
It’s only a multistep process, I will make you understand each step and the chemistry behind it.
Requirements:
Dish soap, salt, rubbing alcohol, a plastic zip bag and coffee filter and breaker or test tube, and a glass rod or straw.
To make the present topic simpler, we interviewed scientists and tried to understand the importance of each step and ingredient. A doctoral fellow, Debayan Baidhya, who wrote many articles for us, made the concepts simpler to understand.
Here are his words, we demonstrate.
Dish soap or washer:
What does dish soap do? It cleans dishes, washes dirt and most importantly, the microorganisms. It neutralizes the cell membrane and washes microbes! Any washing solution or detergents do the same for other cells.
For instance, liquid cleanser removes dead cells, again by neutralizing the cell membrane.
Dishwash soap contains detergents and other chemicals, helping remove the cellular as well as nuclear cover. In case of plants and bacteria, it’s the cell wall, while for eukaryotes it’s the cell membrane.
Not much difference! But the cell membrane is a bit smooth and soft.
In general, this outer cover contains phospholipids, carbohydrates like cellulose, pectin or chitin and protein. Detergents like cationic or anionic detergents easily neutralize these elements and break the cell wall and nuclear envelope.
Alternatives: Laundry detergent, shampoo, body wash, hand soap, liquid cleaner.
Salts:
Adding salt to this makes things better, as the positive charge of the salt reacts with the negative DNA phosphate, making it busy and protecting it from damage.
Alternatives: Baking soda, table salt, Epsom salt and rock salt.
Plastic bag:
Here we use a plastic bag to squeeze strawberries. That’s it. It helps prepare a homogenous lysate.
Alternatives: Resealable sandwich bag, ziploc bag, freezer bag, food wrap, old T-shirt.
Coffee filter:
We isolate the watery DNA solution from the lysate (the smashed strawberries) using the filter paper or a coffee filter.
Alternatives: Paper towel, fine cloth, cheesecloth, tea strainer, cotton pad.
Rubbing alcohol:
To understand the importance of alcohol, we need to do some chemistry. Ready?
DNA is negatively charged. The negative charge reacts with the positive water molecules and makes a crystal clear and watery DNA solution. DNA is usually not visible in this.
On the contrary, alcohol has a higher tendency to react with water, removes bonds between DNA and water, and neutralizes the positive charge of water. DNA can’t find anything to react with and comes up as a cotton thread-like structure– DNA precipitate.
Alternatives: High-proof vodka, ethanol, hand sanitizer, mouthwash, white Rum.
Strawberry DNA extraction process:
- First, prepare the lysis buffer. Take 3 to 5 teaspoons or 5ml liquid soap or any detergent and one teaspoon salt.
- Mix it well and put it aside. Do take care to avoid the foam.
- Take a clean plastic bag and two ripped strawberries. Place strawberries into the zipper bag, pack it tightly and gently smash it or tap it using any object until a homogenous mixture is prepared.
- Do this for one minute.
- Now open the zip bag, add an equal amount of the lysis buffer and close the zip bag again. Mix it for some time (1 min).
- Place it for 5 more minutes to treat the cells well with chemicals.
- Now place the funnel in the test tube or beaker and then the coffee filter. You can even directly place the coffee filter.
- Carefully pour the lysate on the filter paper, place it aside, without any disturbance, to collect the liquid part.
- Drop by drop, the liquid will be collected in the tube after some time.
- Meanwhile, pre-chill the alcohol or rubbing alcohol, and add an equal volume to the liquid we collected.
- Afterward, carefully observe what is happening in the tube.
- When you gently mix the alcohol, smaller DNA threads come out from the solution (we already explained the chemistry). After some time, the precipitated DNA will appear. On top of the solution.
- You can collect it.
After extraction:
This is a fun experiment. It’s a precipitated DNA, but technically useless— can’t be used for amplification or sequencing.
Why?
It’s not pure, as we used only some basic chemicals, and it isn’t highly pure. It contains impurities of protein and RNA, which should be removed to use it downstream.
Strawberry DNA extraction applications:
In particular, this DNA extraction is used for classroom demonstration and activities, at-home experimentation and learning, and understanding DNA analysis.
Wrapping up:
That’s it! We extracted the DNA.
The present demonstration is a basic version of extraction. The actual process is a multi-step experiment that includes multiple chemicals, solutions and reagent preparation.
Post extraction, DNA qualitative and quantitative analysis provides data for whether to use for downstream analysis or not.
This is the basic and popular experimentation that you see on the internet, We will do a lot more with this; we will try different chemicals, techniques and processes and will observe how different types of DNA precipitate we will get, in upcoming articles.
