1. How to Extract DNA from Peas
Step 1
Put in a blender 250ml of peas, a large pinch of salt and 250ml of cold water. Blend for 30 seconds.
The blender separates the pea cells from each other, so you now have a really thin pea-cell soup.
Step 2
Pour the pea-soup mixture through a strainer into a jug.

2. How to Extract DNA from Peas
Step 3
How much pea soup do you have? Add about 1/6 of that amount of liquid detergent and swirl to mix. Let the mixture sit for 5-10 minutes.
The detergent breaks down the cell and nuclear membrane to release the DNA.
Step 4
Pour the mixture into test tubes or small beakers, each about 1/3 full. Using a spatula, add a small amount of protease enzyme.
The protease enzyme breaks down the proteins which bind the DNA.

3. A cell's membranes have two layers of lipid (fat) molecules with proteins going through them.
When detergent comes close to the cell, it surrounds and ‘captures’ the lipids and proteins, breaking down the membranes and releasing the DNA.

4. Each pea cell contains around 3 metres of DNA, but it's only one-millionth of a centimetre wide. To fit all of this DNA into the cells, it needs to be packed efficiently. To solve this problem, DNA is twisted tightly around proteins and clumps together inside cells.
The protease enzyme breaks down these proteins so the DNA is released.

5. How to Extract DNA from Peas
Step 5
Tilt your test tube and slowly pour ethanol into the tube down the side so it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.
Ethanol is less dense than water so it floats on top. The DNA prefers the alcohol layer so moves into this top layer.
Step 6
DNA will rise into the alcohol layer from the pea layer. You can use a wooden splint to draw the DNA out.
The DNA is a long, stringy molecule that likes to clump together.