D.N.A. Extraction Experiment

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We went to the Medical College of Wisconsin for Science Education which is located in Wauwatosa, Wisconsin. The Medical College of Wisconsin sponsors labs for elementary through high school students. We attended the "It's All In Your Genes" molecular genetics lab for fifth and sixth grade students. Shown below is our lab showing how to extract DNA from a banana. We've included all the steps in case you want to do the experiment yourself. You can also visit the Medical College's Web Site to learn about the other programs they offer. If you don't don't know a lot about DNA or would like to learn more, you can visit our DNA Page. The Medical College has given us permission to share this experiment.

 This is what you need


One Half inch slice of banana
One small plastic hook or stir stick
One plastic spoon
One funnel
One doubled piece of cheese cloth or gauze (3" by 3")
One test tube labeled 1 containing a strong detergent
One test tube labeled 2 containing ice cold ethyl alcohol
One empty test tube
One friend or partner

Procedure


1) Place the banana in the cup.

2) Next add the liquid in test tube one. Try to mash the banana into about twenty pieces.

3) Put the cheese cloth into the bottom of the funnel.

4) Now hold the empty test tube under the funnel, if the funnel spout is too big you can hold the test tube at an angle. Pour the banana into the cheese cloth. Lightly mush it down. A liquid will drip into the test tube.

 

 

5) Now you really have to concentrate on this part of the experiment. You need to pour the contents of test tube two slowly into the test tube with the liquid from the banana (1). It should form two layers. A white string or blob will start to appear.


6) You can pull the white material out with the plastic hook. That white stuff is the banana's DNA. Cool, huh?

 

 

 

Here's What Happened


What happened is that the banana's cell walls, cell membranes, and nuclear membranes were dissolved and broken apart by the detergent. The membranes are made out of fats or lipids. The detergent allows the DNA to be released from the cell. The DNA floated out and into our solution.

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