Actually this post will describe how to extract DNA from a banana, a tomato and from yourself. The method is similar for all three.
Extracting DNA samples
I gave the children the choice of extracting DNA from tomatoes, bananas or from themselves. It is very easy to do requiring nothing more than water, salt, surgical spirit, clear washing up liquid, coffee filters, food dye and a tissue sample (salt water washed round in the mouth, smashed banana mixed with salt water, smashed tomato mixed with salt water).
Set Up your Work Stations
Set up three different work stations with all the need equipment to extract the DNA, including an instruction sheet:
Create a Tissue Sample
This will be a sample of salt water which has millions of cells suspended in it. To do this, mix a teaspoon of salt with half a cup of bottled water:
Smash the banana or tomato flesh in a zip lock bag. Add salt water solution and mix carefully. For your own tissue sample use the salt water as a mouth water and gargle for one minute suspending cheek cells in the water and carefully spit into a clear beaker:
Add a half a teaspoon of dish soap to the zip lock bags (or if doing your own DNA add a couple of drops to the gargled suspension in the beaker). Mix gently trying not to create too much foam. The soap acts to break down the cell membrane releasing the DNA into the suspension:
Pour the contents of the zip lock bags through a coffee filter sitting over a funnel over a clear glass beaker. Leave awhile whilst it collects a liquid suspension of water, soap and tomato or banana DNA:
Extract the DNA
In a separate cup mix 100mls of surgical spirit and a few drops of food colouring:
Gently pour the alcohol down the side of the beaker containing the suspended tissue sample (tip beaker):
It should form a layer on top of the sample. Leave for a few minutes:
At this point you should notice a few strands or clumps of a white substance. These are the DNA strands clumping together. Using a stirrer you may be able to pick up some of the strands:
You have extracted your DNA!
Cool. Forensic scientists in the making.
Yup. Soon we’ll be able to discover who is stealing all the goodies from the cupboard using DNA profiling….!!
Hi. My daughter is studying DNA right now too! What your kids do with the DNA they extracted?
We made slides and looked at it under the microscope, but didn’t really see a whole lot. Our microscope really needs a stronger resolution. If you look at Marie’s comment below, her daughter put it in a necklace!
You had really good success with this. We tried it once and totally failed – good to see someone doing it right 🙂
Both the tomato and banana really worked, and left overnight the banana DNA formed clumps. The cheek DNA wasn’t as successful. It was still a huge amount of fun!
That is so cool! Pea extracted her DNA at a science day camp years ago and kept it in a little bottle attached to a necklace 🙂 She was a little grossed out when she found it again in a box of odds and ends! Now I want the four of us to try extracting DNA too (but not save it or wear it) .
I laughed at the wearing it part. Yuk! Although when I was a child that would have been totally cool!
The shot of the twin gargling, she has this look saying “Mom, why are you taking my picture?” Poor girl.
In fact she was hating every minute of gargling salt water! My girls never mind me taking photos. T is another matter all together. He puts up with it.
Love this science application! Thanks for sharing the process.
No problem, my pleasure!
We did this also, but I think you had a better result with the human DNA. These experiments are lots of fun. Your children look like they really enjoy them.
All of them really love science, especially if I am not requiring them to write anything!
Great homeschool-science! We need to try it ourselves.
It was more successful than I had been led to believe. And so easy.