Use a toothpick to fish out the gooey strands of banana DNA. Photo/supplied
Does a banana have DNA?
Yes, it sure does. Like all living things, a banana has a unique set of DNA, and today we're going to see what it looks like. Get ready to do some DNA extracting!
Introduction
All living things are made up of cells, and within the nucleus
of each cell is a stringy substance called DNA, which stands for deoxyribonucleic acid. DNA contains the biological instructions that make each species and each of us unique.
We can't see a single cell or the DNA inside it with our eyes - scientists need very powerful microscopes and other equipment to do that. But we can extract DNA from millions of cells, and view it without a microscope. Let's have a go!
What you need
* Banana
* Water
* Detergent
* Methylated spirits, chilled
* Small disposable plastic narrow container, preferably with lid.
What to do
1. Blend half the banana with 1?2 cup of water until smooth.
2. Half fill your container with the banana mixture (you may not need all of it).
3. Add around 10 drops of detergent to the banana mixture.
4. Put on the lid and gently shake the container (this will break open the cells and release the DNA).
5. Carefully pour around 20 to 30mls of the chilled methylated spirits (also known as denatured alcohol) into the banana mixture. The methylated spirits should sit on top of the banana mixture.
6. Let the mixture sit for a few minutes; you should soon see whitish material forming between the two layers of liquid. This is banana DNA! Use a toothpick to fish out the gooey strands and look at them under a microscope, if you have one.
What's happening?
The banana is made up of millions of cells which contain DNA. To release the DNA, we need to break down the plant matter, then break open the cell.
Squashing or pureeing the banana takes care of the first breaking down stage. Adding the detergent then helps to break down the outer membranes of the cells, and, in doing so, releases the DNA.
Because the DNA is soluble in water, something else is needed to separate it from the mixture. That's where the methylated spirits (alcohol) comes in - it draws out the DNA from the banana/water mixture. The DNA can't dissolve in the alcohol so clumps together between the two layers of liquid. The methylated spirits is lighter and less dense than the banana/water mixture so sits on top.
Other fruits, such as strawberries and kiwifruit, work really well in this experiment.
Did you know?
* Every human shares 99 per cent of his or her DNA with every other person.
* If you unravelled all the DNA molecules in your body and put them end to end, they would reach from the Earth to the sun and back several times.
* A parent and child share 99.5 per cent of the same DNA.
* You have 98 per cent of your DNA in common with a chimpanzee.
Here's a cool video showing how DNA replicates:
http://www.sciencekids.co.nz/videos/biology/dnareplication.html
The House of Science Tauranga is a charitable trust which exists to connect and resource the local science community to celebrate the power and potential of science. Contact Chris Duggan on 027 337 9342 or see www.houseofscience.org.nz for more information.