Year 5 Science Experiment

Extract DNA from a Strawberry

See real DNA with your own eyes! Extract the genetic code from a strawberry using simple kitchen supplies.

Adult supervision recommended for younger children.

This experiment uses rubbing alcohol (isopropyl alcohol) which should be handled by an adult. The extracted DNA is safe to touch but not to eat.

Safety First!

• Rubbing alcohol is flammable — keep away from heat and flames.
• Do not drink or taste the rubbing alcohol or the extraction mixture.
• An adult should handle the rubbing alcohol.
• Wash hands thoroughly after the experiment.

You Will Need

✓ 1-2 fresh strawberries

✓ A zip-lock plastic bag

✓ 1 tablespoon of dishwashing liquid

✓ 1 teaspoon of salt

✓ About 1/3 cup of warm water

✓ Rubbing alcohol (isopropyl) — kept in the freezer for 30 min beforehand

✓ A coffee filter or piece of cheesecloth

✓ A clear cup or glass

✓ A wooden skewer or chopstick

Step-by-Step Instructions

Make the Extraction Solution

In a small bowl, mix together the warm water, dishwashing liquid, and salt. Stir gently until the salt dissolves. Try not to make too many bubbles.

Mush the Strawberry

Remove the green stem from the strawberry and place it in the zip-lock bag. Seal the bag (push out extra air) and squish the strawberry with your fingers for about 2 minutes until it is a smooth pulp. You want to break apart as many cells as possible.

Add the Extraction Solution

Open the zip-lock bag and pour in the extraction solution. Seal the bag again and gently mix by squishing for another minute. The soap is breaking open the cell membranes to release the DNA.

Filter the Mixture

Place the coffee filter over the clear cup and carefully pour the strawberry mixture through it. Let it drip through slowly — you want only the liquid, not the chunky bits. You should get about 2-3 cm of pink liquid in the cup.

Add the Cold Alcohol (Adult Step)

Have an adult carefully pour ice-cold rubbing alcohol down the side of the cup so it forms a layer on top of the strawberry liquid. Pour slowly — you want the alcohol to sit on top of the pink liquid, not mix in. Add about the same amount of alcohol as strawberry liquid.

Watch for DNA!

Wait 2-3 minutes and watch the layer where the alcohol meets the strawberry liquid. You should see white, stringy, cloudy strands forming and rising into the alcohol layer. That is real DNA! Use a skewer or chopstick to gently spool up the DNA strands.

What Happened?

You just extracted real DNA — the molecule that contains the genetic instructions for every living thing! The white, stringy substance you can see is billions of DNA molecules clumped together.

Here is what each ingredient did:

• Mushing the strawberry broke apart the tissue into individual cells.
• Dish soap broke open the cell membranes (which are made of fat) to release the contents, including DNA.
• Salt helped the DNA strands clump together by neutralising their electrical charge.
• Cold rubbing alcohol caused the DNA to precipitate (come out of solution) because DNA does not dissolve in alcohol. The cold temperature helps it clump more.

Strawberries are perfect for this experiment because they have eight copies of each chromosome (they are octoploid), meaning they contain a lot more DNA per cell than most fruits!

The Science Behind It

DNA stands for Deoxyribonucleic Acid. It is a long, twisted molecule found inside the nucleus of almost every living cell. DNA contains the instructions (genes) that tell cells how to build and operate a living organism.

DNA is shaped like a twisted ladder called a double helix. If you could unwind the DNA from a single human cell and stretch it out straight, it would be about 2 metres long — but it is coiled up so tightly that it fits inside a cell nucleus that is too small to see!

Every living thing — plants, animals, fungi, bacteria — has DNA. You share about 60% of your DNA with a strawberry and about 99% with other humans. The small differences in our DNA are what make each of us unique.

Scientists extract DNA in laboratories using a very similar process (just with more precise chemicals) to study genetics, solve crimes, diagnose diseases, and even trace family ancestry.

Australian Curriculum link: Science Year 5 — Living things have structural features and adaptations that help them survive in their environment (AC9S5U01). The growth and survival of living things are affected by physical conditions. Biological sciences: cells are the basic units of living things.

Think About It

If every cell in your body has the same DNA, why do your skin cells look so different from your brain cells or blood cells?

You share 60% of your DNA with a strawberry. What does this tell you about how life on Earth is connected?

How might extracting DNA be useful for solving crimes? What about for medicine?

Could you try this experiment with other fruits or vegetables? Which ones might give you the most DNA? Why?

Key Concepts Summary

● DNA (Deoxyribonucleic Acid) is the molecule that carries genetic instructions in all living things.
● DNA is found inside the nucleus of cells and is shaped like a double helix (twisted ladder).
● Every living thing — from strawberries to humans — contains DNA.
● Soap breaks open cell membranes, salt helps DNA clump together, and cold alcohol makes DNA come out of solution.
● Scientists use DNA extraction for medical research, forensics, and understanding genetics.

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