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Basic science: understanding experiments
Basic science: understanding experiments

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4.1 Experiment 5: Kiwi experiment

Figure 1

In humans, the DNA molecule is very long and thin. It is about 2.5×10−9m across, yet if it were stretched out, it would reach up to 2 or 3 metres in length. Within the cell, the molecule is twisted and coiled, like earphone cables kept in a coat pocket. In fact, there is enough DNA in your cells to reach to the Sun and back about 65 times.

Fortunately for us, this experiment won’t require you to build a spaceship and test that fact. For this experiment, you are going to use some fairly common materials to extract the DNA from the cells of a kiwi fruit. Once the DNA is isolated and clumped together, there will be enough for you to see without microscopes or high-tech equipment and it can also be carefully removed with nothing more than a paper clip.

We will keep referring to a kiwi fruit throughout the week, as this is an easy example to obtain and to work with, but you can use other soft fruits if you wish. Remember, you will then be altering a variable, and should be ready to discuss how it affects your results.

To carry out this experiment, you will need:

  • a kiwi fruit (or another fruit of your choice)
  • a peeler/knife (to remove the skin/peel)
  • a fork
  • methylated spirits, chilled in freezer for 30 minutes (or vodka/strong white rum)
  • a fine sieve or filter paper
  • a couple of bowls
  • salt
  • tap water
  • warm water
  • washing-up liquid
  • teaspoon
  • measuring beaker
  • a couple of glasses
  • a paperclip.

Remember, methylated spirits are extremely hazardous and should only be used by adults or with adult supervision.