DNA extraction of a kiwi plant in The Homework Club kitchen

Lesson devised by Graham Huges who has taught maths, science, computers and biology at The Homework Club for the last two years.

Graham Hughes is studying a PhD in Bioinformatics at UCD. He is interested in Science, particularly biology and believes with the correct approach, science can be made accessible and enjoyable to all students. Graham also works on computer techniques to make students more motivated to do well in mathematics.

DNA, DNA come out and play…

If you were to zoom in closely on a piece of your skin, you would see it is made up of millions of cells. If you were to zoom in on a cell you would see it is made up of smaller organelles. If you were to zoom in on certain organelles you would see that they contain DNA. DNA stands for DeoxyriboNucleic Acid and is made up of long strands of the letters A,T,G and C. The arrangement of all these letters in your DNA is the ‘recipe’ for you.

All animals and plants have DNA in their cells. By using household materials we managed to extract and view some of the DNA in a kiwi! Even though you cannot even see kiwi cells with the naked eye, with the tricks of the trade, we can gather enough DNA to make it easily visible. All it takes is a little chemistry…

Firstly we need to make an ‘extraction buffer’. This involved putting water in a plastic cup, adding 2 small sachets of salt and putting 2 squirts of hand soap, giving it a good mix. The soap breaks up the fatty kiwi cell membranes and the salt makes the DNA clump together.

Next, we mashed up some of the kiwi (the mashier, the better!) and added this mash to the extraction buffer. Kiwi’s are ideal as they have their own special enzymes that break down proteins attached to the DNA.

The kiwi-extraction mix needs to be placed at 60 degrees to break down the cell wall letting the DNA out. To achieve this, we boiled some water in the homework club kettle,letting it cool a little. We incubated our cups in this water for 15 minutes. Afterwards, the mixture was poured over some coffee filter paper to remove the chunks of kiwi.

The final stage of the DNA extraction involved adding some ice cold methylated spirits by pouring it slowly down the side. Since it is less dense than the mixture, it forms a liquid layer that the DNA floats in. The transluscent jelly-like stuff we now see floating in this layer is the kiwi DNA.

By using very basic materials, a kiwi and some methylated spirits, we managed to isolate some DNA in our homework club kitchen – something done a large scale in research labs across the world!