All living things have DNA; animals, plants, fungi, even teeny tiny bacteria. It’s what makes us who we are. Year 4 had a look at some real DNA that they extracted from strawberries.
- Two strawberries
- Surgical spirit (available in any chemist)
- Washing up liquid
- Table salt
- Pestle and mortar
- Plastic cups or beakers
- Small glass
- Small sieve
- Tweezers or cocktail sticks
What to do:
- Put the surgical spirit in the freezer at least an hour before you start. Leave it there until step 8.
- Remove the leaves from the strawberries and put the fruits in the bag.
- Mash the strawberries! This is the fun bit…don’t break the bag though. You can squash the strawberries in a pestle and mortar (or bowl and spoon!) instead to avoid plastic waste.
- To make the extraction mixture which will break open the cells and let the DNA escape: measure 90ml water into a beaker or cup, add a teaspoon of salt and two teaspoons of washing up liquid. Stir slowly…we want it mixed but not bubbly.
- Add 4 teaspoons of the extraction mixture to your bag of mashed up strawberries. Mix GENTLY.
- Sieve the strawberries into a clean beaker.
- Pour this into your small glass. The DNA is now free in the mixture instead of being stuck inside cells but it is VERY thin so we can’t see it.
- Carefully pour some cold surgical spirit on top of the strawberry liquid. You should see a cloudy white layer appear, this the DNA! The alcohol makes it clump together so you can see it. You can pull this out with tweezers or a cocktail stick to have a proper look.
All cellular life on Earth has DNA. Some viruses have another molecule called RNA instead but it’s a bit of tricky question to decide if viruses are actually alive anyway. Of course, we don’t know if any lifeforms that may exist on other planets have DNA or something else entirely. Year 4 are enjoying researching and investigating this topic in our ‘Journeys & Discovery’ theme of investigation this term.