Friday, 20 May 2011


Cells are composed of nuclei, and nucleus is considered the largest single structure within the cell. It is further composed of separate structures called chromosomes which are responsible to carry information for reproduction or for sort of genetic analysis in laboratories. These chromosomes are made of a more complex polymer called DNA or Deoxyribonucleic acid. Although DNA is a very large molecule, you could not see it with your naked eye, unless you know and you have a great deal with it.

The Fruity DNA experiment will teach you the procedure how to collect large number of chromosomes using common fruits. This is just a simple laboratory experiment for a biology class.


4 x 100ml beaker
2 x 250ml beaker
1 x 500ml beaker

stop watch
fruits (preferably fruits that are slurry when crushed like KIWI, or tomato, or strawberry)
filter paper
plastic funnel
4.0 grams sodium chloride (common salt, fine ones)
measuring cylinders
pestle and mortar
washing-up liquid
stirring rod (preferably glass)
ice in a plastic bowl
wire hook (#22 )
ethanol (make sure it is inside the freezer over night and before using)

Note: Peel the fruit and slice into smaller dices. Allow the kettle to boil before you start the procedures. Try this first before introducing to your students, and in my experiments, I find it best to put more ethanol into the mixture.

1. Weigh 4.0 grams of common salt and put into the 250ml beaker.
2. Add 15ml of washing-up into the same beaker and stir thoroughly to make sure the salt is dissolved completely. Then put this mixture to one side.
3. Crush the fruit using the mortar and pestle until it becomes mushy and ‘slurry’, put this in another 250ml beaker.
4. Add an equal volume of the mixture you made in procedure 2 to the mashed up fruit in procedure 3.
5. Put hot water into the 500ml beaker and place the whole beaker you prepared in procedure 4. (If water bath is available, set it at 60 degrees)
6. Leave this to stand for the next 10 to 15 minutes.
7. Prepare the filter funnel and the filter paper, when 10 to 15 minutes has elapsed, filter the mixture and collect the filtrate using the 100ml beaker. You should have a pure liquid into the 100ml beaker.
8. Hold the beaker properly and tilt it slightly, very slowly put as much as you have filtrate the ice cold ethanol down the side of the beaker.
9. Do not stir, leave it to settle for a minute. You should be able to see some layer between the ethanol and the filtrate. This is the fruit DNA, and if possible, use the wire hook to pick up some of it.

Guide Questions:

What’s the use of ETHANOL?
Why do you need to mash up the fruit?
What’s the washing-up liquid for?
What is the role of sodium chloride?


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