Fruits DNA Extraction

In recent years, it is not uncommon to read articles on DNA in both scientific and popular magazines. DNA is regularly mentioned in the news and is often featured in TV detective or crime-scene investigation dramas. DNA, also known as DeoxyriboNucleic Acid, is a long molecule that holds the genetic information for all living beings, be it vegetable, animal or a simple microorganisms. It is capable of copying itself and can synthesize RNA (RiboNucleic Acid). In more evolved or complex forms of life, DNA is contained in the nucleus of the cells. Except for the red blood cells of mammalians, which are devoid of a nuclei, all cells of a living being have their own DNA. The cells of an organism use certain parts of the DNA molecule, or genes, to produce the proteins they need to function. In this article, I describe a simple experiment that will allow you to extract a bit of DNA from a banana, however, you can also try it using other fruits and even vegetables. It is an experiment that can be performed both at home and in a school laboratory.

The procedure described below exploits the fact that the external membrane of cells and that of their nuclei are composed of fatty substances that can be broken down using a simple detergent. The first operation in this procedure is to break-up the fruit into a pulp or mush so that the cells are separated each from other as much as possible thereby exposing them to the action of the detergent. Secondly, the detergent is added to the pulp of the fruit so as to release the DNA from the cell membranes, which encapsulate it. Thirdly, it is necessary to filter the mixture to separate the nucleic acid from the remains of the cellular membranes. Finally, the DNA is precipitated in alcohol where it becomes visible. The DNA you obtain using this procedure can be observed with a microscope and can be used for other experiments like electrophoresis or other experiments.

Results, Questions:
1. What does the salt do? (Salt provides the DNA with a favorable environment; it contributes positively charged atoms that neutralize the normal negative charge of DNA.)

2. What does the blender do? (help break down the cell walls)

3. When you mix the blended cell source with the soap, what is happening? (In the experiment, the enzymes in the soap are breaking down the lipid molecules of the cell and nuclear membranes, releasing the contents of the cell, including the DNA. These enzymes in the soap are what break down grease while washing dishes.)

4. What does the alcohol do? Why does the DNA rise to the top after adding alcohol? (DNA will not dissolve in this alcohol, so the DNA comes out of the solution, or precipitates. It is less dense than water or cell scum--which is what settles to the bottom of the glass--so it floats up into the alcohol layer, where you see it as a snotty, string-like substance, with small bubbles formed on it.)

5. If you try a seed food such as peas, there will be more protein residue in the liquid. Why?(Because protein is stored in them for the nutrition of the new plant.)

6. Why can’t you see the double helix? (It is too small to be seen with the naked eye. What you extracted is millions of strands of DNA.)

7. What part of the cell did the DNA come from? (99% is from the nucleus.)

Watermelon DNA extraction

Papaya DNA extraction 

Mango DNA extraction