Miss LM 01/15/2007

DNA Extraction

A. Purpose:

The object of this experiment is to extract DNA from peas to study what DNA looks like on a macroscopic scale. Most of the time, DNA can only be seen through a microscope. This experiment will offer another way to view DNA that does not require a microscope.

A DNA molecule is made of chemical building blocks called nucleotides. The four types of nucleotides in DNA are called adenine (A), thymine (T), guanine (G), and cytosine (C). (Koshland) A strand of DNA is composed of two long strands of A, T, G, and C. If on one side of the strand there is adenine, then thymine will be directly opposite the adenine. Likewise, if there is guanine on one side, then there will be cytosine on the other side. Thus, if one strand of DNA is known, then the other will be known as well. The second strand will merely be the opposite of the first strand.

A, T, C, and G, the nucleotides in DNA, can be thought of as a 4-letter alphabet. Two adjacent groups consisting of three nucleotides code for one amino acid. The groups of three nucleotides are called a codon. (Access) This genetic code, which was cracked in the 1960s, is universal in almost all organisms. Without the knowledge of this code, most modern biotechnology would not exist.

This experiment hopes to show how DNA is extracted from an object. Usually DNA is only viewed through a microscope. This experiment will demonstrate how DNA can be extracted from a cell and what steps must be taken to break down the cells that encompass the DNA.

This topic is of interest to scientists because studying DNA is a way to learn about the DNA and the DNA's surroundings. Knowledge about DNA is useful to scientists because those scientists can then learn more about the object that the DNA came from. If a scientist knows more about how DNA works, then said scientist will know more about how a human body works. This knowledge can be passed on to doctors who can then create antibiotics that will help cure sick people and prevent healthy people from becoming ill.

Hypothesis: If the plasma membrane and proteins of a cell can be destroyed, then DNA can be extracted and viewed either macroscopically or microscopically.

B. Equipment:

1. Blender
2. Clear liquid hand soap
3. Salt
4. Water
5. Strainer
6. A glass
7. Meat tenderizer
8. Rubbing alcohol
9. ½ cup split peas
10. Measuring cups
11. Flashlight

C. Procedure:

1. Dissolve ¼ teaspoon of salt in one cup of water.
2. Place the peas and saltwater in the blender and blend for roughly 20 seconds.
3. Hold the strainer over the cup and slowly pour the contents of the blender into the cup so that the pea mixture drips into the cup.
4. Add two tablespoons of soap to the pea mixture.
5. Gently stir the contents in the glass and let the pea mixture sit for 10 minutes.
6. After 10 minutes, add ¼ teaspoon of meat tenderizer and mix very gently.
7. Slowly add as much rubbing alcohol as there is liquid in the glass. DO NOT STIR.
8. Shine the flashlight on the contents of the glass and view the pea mixture.
9. Clean up the mess.

D. Observations:

1. When the peas and saltwater were blended in the blender, 30 rather than 20 seconds was needed to more thoroughly chop up the peas.
2. When pouring the blended mixture through the strainer into the glass, the mixture was hard to pour slowly. Most of the pea mixture came out all at once.
3. When the soap was added to the pea mixture, the mixture became thicker.
4. The meat tenderizer did not want to dissolve in the pea mixture. The tenderizer wanted to stick to the measuring spoon and when the tenderizer finally fell off the spoon, the tenderizer clumped together.
5. When the rubbing alcohol was added, the alcohol first soaked down past the pea mixture. The alcohol quickly rose past the surface and rested above the pea mixture.
6. Tiny bubbles rose through the mixture like carbonation.
7. A whitish substance that looked like a shed snakeskin stuck to the side of the glass.
8. The pea mixture became a lighter shade of green when the alcohol was added.
9. There were a few large bubbles holding onto the pea part of the mixture and floating beneath the surface of alcohol. Those bubbles did not pop.
10. Tiny white strands of DNA rested just below the surface of alcohol.

E. Conclusions:

Blending the peas separated the pea cells from each other. The reason the soap was added was to dissolve the phospholipids in the plasma membrane of the pea cells. This will in turn destroy the plasma membrane and open the cells, letting the contents of the cells flow into the solution. The meat tenderizer contained enzymes that would destroy the proteins that coat the DNA. This exposes the strands of DNA. Alcohol is less dense than the pea mixture; that is the reason the alcohol rested on top of the pea mixture. Since alcohol is less dense, the white strands of DNA were able to float through the pea mixture and settle in the alcohol. The hypothesis was proved true in this experiment because the plasma membrane and proteins of a cell were destroyed and DNA was viewed macroscopically.

One way to improve the experiment would be for the book to state exactly what type of soap or detergent works best for the experiment. Another idea would be to pour the contents of the blender into a measuring cup designed for pouring liquids before pouring the contents into the glass. This step will remove the thick pea clumps at the bottom of the blender that are too big to go through the strainer; also, the liquid is easier to pour from a measuring cup rather than the blender. One last idea for improving the experiment would be to pour the rubbing alcohol into a measuring cup before adding it to the pea mixture. When adding the alcohol straight from the bottle, the alcohol pours much too fast.

One idea for further research would be to use something besides peas to extract DNA from. Another idea would be to try using different types of soap or detergent to mix in the peas, or to try products other than soap that dissolve phospholipids just as well. Another idea for further research would be to examine the extracted DNA under a microscope.

F. Bibliography:

Access Excellence @ the National Health Museum. Reading the Messages in Genes. 1999.

Domain: http://www.accessexcellence.org

Document: /RC/AB/BC/Reading_Messages_in_Genes.html

Koshland Jr., Daniel E.; Alberts, Bruce M.; Botstein, David; Somerville, Christopher R.; Staskawicz, Brian J. Putting DNA to Work. 2006.

Domain: http://www.koshlandsciencemuseum.org

Document: /exhibitdna/seq01.jsp

Rosenoff, Steven. Classroom/Internet Lecture. January 2007.

Wile, Dr. Jay. L. and Durnell, Marilyn F. Exploring Creation with Biology, 2^nd Ed. Apologia Educational Ministries, Inc. 2005