Raw Wheat Germ Spoon Test Tube
Distilled Water Detergent Solution Salt Solution
Rubbing Alcohol Bent Paper Clip
Overview and Purpose
In this investigation, you will work with several simple chemicals that can break down the membranes
of a cell. Each yeast cell has two membranes; cell and nuclear. DNA is found in the second. To see the DNA,
we have to break open these two membranes. We use a detergent solution to do this. The same way
detergent removes grease, is the same way we are going to get rid of the membranes.
Soap molecules and grease molecules are made of two parts: Heads which like water and Tails which
HATE water. Both soap and grease molecules organize themselves in bubbles (spheres) with heads outside to
face the water and tails inside to hide from the water. When soap comes close to grease, it captures it,
forming a greasy soapy ball. A cell's membranes have two layers of lipid (fat) molecules with proteins going
through them. Fats act like grease in detergent. When detergent comes close to the cell, it captures the lipids
(fats) and proteins.
1. Place a small scoop of wheat germ in a test tube. The wheat germ should be about 1 cm high in the
2. Add enough distilled water to wet and cover all of the wheat in the test tube
3. Add 30 drops of detergent solution to the test tube
4. For 3 minutes, gently swirl the test tube contents by rotation your wrist while holding the tube. Try
not to make bubbles. (See picture 1)
5. Add 30 drops of the salt solution to the test tube, and swirl for one more minute.
6. Hold the test tube tilted at an angle. Slowly add alcohol so that it runs down the inside of the test
tube (see picture 2). Add enough alcohol to double the total volume you started with. Let the test
tube stand for 2 minutes.
7. Watch for a stringy, cloudy material to rise up from the bottom layer into the alcohol layer. This is
8. Use a bent paper clip to remove some DNA. Be careful to probe only the alcohol layer and not
disturb the material at the bottom of the test tube. (see picture 3)
Observe and Analyze
1. How do your observations of the DNA you just extracted compare with what you know about the
structure of DNA? Record these comparisons in the Table below.
Properties of DNA Observations of Wheat DNA
2. What type of organism is wheat? Where is the DNA located in a wheat germ cell?
3. What was the purpose of the detergent in this activity?
4. What might happen if the wheat germ was not mixed properly with the detergent solution?
5. Would this experiment work with cells from other organisms, such as bananas, onions, etc? Why or
6. Would DNA from a single cell be visible to the naked eye?