DNA Extraction Banana

Banana DNA Extraction

This DNA extraction is simple and works every time but the DNA is not pure. Some of the protein is still present. It is nice however because the students get to see and hold in their hand the substance they have been studying that seems so abstract and hard to believe it even exists.

Materials for each group of students:

graduated cylinder
beakers 100ml and 2x250ml (or jars that same size)
liquid dishwashing detergent (clear solution works better than cloudy)
1/2 of a banana
knife
mortar and pestle
salt
coffee filter
rubber band
test tube
COLD 95% ethanol (this is something that you can't substitute)
wooden splint
refrigerator

Procedure:

Make a 10% solution of dishwashing detergent in one of your 250ml beakers (make enough to fill the mortar half way)
Slice the banana into the mortar
Add the 10% detergent solution to cover the fruit
Add a pinch of salt
Grind the banana in the soap solution until there are no lumps (this is the hardest part, have the students take turns)
Fasten a coffee filter to the 250 ml beaker with a rubber band so there is room for the fruit to be poured into the filter
Pour the fruit and soap mixture into the filter and place in a cold place to filter
Clean up your lab area while you are waiting for the filtering to complete
Remove the filter and through away the contents
Pour enough of the liquid into a test tube to fill it 2 cm high
Add twice the volume of 95% ethanol (try to layer the alcohol on top by gently pouring it down the side of the test tube)
The DNA will precipitate in the boundary between the alcohol and the banana mixture as a cloudy mass
Spool the DNA onto your wooden splint

Some addition protocols for DNA extractions:
How to Extract DNA from Anything Living This site has a great explanation for each step along with pictures!
DNA Extraction from Wheat Germ This site has a method that never fails to give you a large amount of DNA

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