DNA Extraction from Wheat Germ

Problem: How do you extract DNA from living material?

Materials: 2 test tubes, wheat germ, hot water, stirrer, detergent, 95% alcohol

Procedure:

1. Place 1 gram of raw wheat germ in a 50 ml test tube.

2. Add 20 ml of hot water and mix constantly for 3 minutes.

3. Add 1 ml of detergent and mix gently every minute for 5 minutes. Try not to create foam.

4. Use an eyedropper, pipette, or piece of paper towel to remove any foam from the top of the solution. Pour the water/detergent solution slowly into a clean test tube leaving behind the wheat germ.

5. Tilt the test tube at an angle. Using a pipette, SLOWLY pour 1 ml of alcohol down the side so that it forms a layer on top of the water/detergent solution. DO NOT MIX THE TWO LAYERS TOGETHER.

6. DNA will precipitate out at the water/alcohol interface (the boundary between the water and the alcohol). Therefore it is crucial to pour the alcohol VERY slowly so that it forms a layer.

7. Let the test tube sit for a few minutes. White, stringy, filmy DNA will begin to appear where the water and alcohol meet. If you let the preparation sit for 15 minutes, the DNA will float to the surface.

8. Use a glass or plastic stirrer to collect the DNA and place in a small tube.

DNA Extraction Lab Questions:

1. Which part of the wheat seed is targeted for DNA extraction?

2. On a cellular level, what two events happen when hot water is added?

3. With regard to the structure of the cell membrane/nuclear membrane, what was the function of the added detergent in this process? Be specific.

4. What purpose does the alcohol serve as the final step of the process?

5. What would happen if we mixed the alcohol into the solution rather than layering it on top?