DNA extractions in the Learning Centre

This term, Stage 4 and 5 Science students in the Learning Centre have been exploring the topic of ‘Evolution’, and have been enjoying learning all about DNA. Students learnt that DNA is present in every cell of living organisms, and how it determines the genetic traits of an individual organism. With eager students wanting to know more, what better way to explore DNA than to extract it and view it with the naked eye?!

Through a practical experiment involving large, red strawberries, students experienced a hands-on extraction of DNA. They learnt that strawberries – unlike humans, who have two sets of chromosomes – are octoploid, meaning that their cells each have eight duplicate copies of each chromosome. This gives the strawberry cells a large quantity of DNA, which means it is relatively easy to extract a large visible amount of.

The students had a great time crushing the strawberries, and following the scientific experiment method to extract DNA!

Method:

  1. Wash the strawberry and remove the green sepals.
  2. Place the strawberry in a zip lock bag, seal it and crush it with your hand.
  3. Add 2 teaspoons of the DNA extraction buffer to the bag, seal it and squeeze to mix for about 1 minute.
  4. Place a funnel in the test tube. Place the strip of gauze in the funnel.
  5. Pour the strawberry buffer mixture into the funnel so it is filtered into the test tube.
  6. Carefully pour ice cold ethanol into the tube until it is about half full. The ethanol will form a layer on top of the liquid that came through the gauze. DO NOT SHAKE.
  7. Keep the tube still and hold it at eye level. Watch what happens and record your observations below.
  8. Scoop out the DNA carefully using the cocktail stick.
  9. Spread the DNA out on a piece of black card to view it and record your observations below.