With Halloween approaching, have you caught yourself wondering what you’re going to do with all your pumpkins after the big day?
We’ve created a fun experiment to entertain your mini scientists, follow our easy step by step guide to extracting the DNA from your leftover pumpkin.
Blend (or grind) your pumpkin until it looks like puree (like a smoothie), small lumps and bumps are fine but get it as smooth as you can. You might need to add a little bit of water to help the blending go faster.
-This step helps to break up the cellulose fibers holding your pumpkin cells together, which will help the next step work its magic.
Combine ½ cup of water with 2 teaspoons of dish soap and 1 teaspoon of table salt. Mix until the salt is dissolved.
In a new clean cup, add 2-3 tablespoons of the solution you’ve just made to 1 tablespoon of pulverized pumpkin paste and stir it altogether, until it looks soupy. If it doesn’t look soupy enough, add more of your solution.
-This step is important because the detergent in the dish soap will help to break open the cell membrane, setting the DNA free into the water. This is a process we call ‘lysis’. The solution you made using the salt, water and soap is called your ‘lysis solution’!
How does it work?
Detergent molecules perform the really important task of separating fats and water when you’re washing up, which is what cleans the oil and things off your greasy frying pans!
In the pumpkin mix you’ve just made, it helps to separate the fat part of the pumpkin cell membrane, breaking it up, allowing the DNA to get free. This is because plant cell walls are formed of cellulose, but inside the cellulose wall is another cell wall called the cell membrane. It is made up of fats, sugars, and salts, and forms two layers, with the fat molecules on the inside, where they can stay away from water.
Detergent has molecules that like fats at one end, and water at the other end. The end of the molecule that likes fat sticks to the grease on your dishes, and the other end sticks to the water in the sink. As you scrub, the grease breaks up into smaller and smaller droplets, and the detergent surrounds them so that they don’t coalesce back together. Then you rinse them down the drain.
Strain your pumpkin mix into a new clean glass (this is when it would best to use the most narrow tall glass you have), by placing your filter over the glass and pouring the pumpkin mix on top. Do it slowly so there’s no spillages!
Get your rubbing alcohol from the freezer. Tilt the glass with your pumpkin mix and pour the rubbing alcohol onto it very slowly- it should form a layer on top of your pumpkin mix.
Leave it standing still for a minute. You should start to see white cloudy things appear between the rubbing alcohol and the mixture- this gooey stuff is your pumpkin DNA!
You can repeat this experiment with lots of different fruits and veg that you’ll find in your fridge, to help teach your mini scientist about the amazing world of DNA that makes up everything around them!
Help us celebrate #STEMday on November 8th by sharing the results of your experiment on social media to encourage other young scientists! Don’t forget to tag us in your pictures (@dolomitebio)