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DNA EXTRACTION FROM WHEAT GERM


DNA EXTRACTION FROM WHEAT GERM


Would you like to see LOTS of DNA?

This method yields large quantities of DNA that can easily be collected.

Here's what you'll need for each DNA extraction:

Materials Needed:

Raw wheat germ - 1 gram or 1 teaspoon.
Wheat germ can be purchased at a health food store or some large supermarkets; toasted wheat germ does not work.

Liquid detergent - 1 ml or a scant 1/4 teaspoon
The following liquid soap products have been tested and found to work well for this DNA extraction protocol: Lemon Fresh Joy, Woolite, Ivory, Shaper, Arm & Hammer, Herbal Essence shower gel by Clairol, Tide, Dish Drops, Kool Wash, Cheer, Sunlight Dish Soap, Dawn, Delicate, All, and Ultra Dawn.

The following liquid products do not work well: Life Tree, Shout, Shaklee, Sunlight Dishwasher, and LOC. Powdered detergents also do not produce good results with this protocol.

Alcohol - 14 ml or 1 tablespoon
70% isopropyl alcohol ("Rubbing alcohol") is the least expensive since it can be purchased at a grocery store or pharmacy. However, it contains a higher percentage of water, making it slightly more difficult to precipitate the DNA.

95% ethyl alcohol and Everclear grain alcohol (which is 95% alcohol) both work equally well. The DNA is easy to collect.

50-60° Celsius tap water - 20 ml or 1 tablespoon
Do not use water hotter than 50-60° C. The water will cool during the extraction procedure, but this does not matter. Test your tap water -- it may be hot enough right from the tap.

50 ml test tube
Capped test tube, beaker or spice jar.

Graduated cylinder,
Measuring spoons, or other measuring devices.

Wooden applicator stick,
Glass stirring rod/hook, paper clip hook, or shish kebob skewer for stirring and collecting the mixture.

Eyedropper,
Pasteur pipette and bulb, or pieces of paper towel - may be needed to remove foam

Sealable container (optional),
Such as a tube, vial or jar to store DNA.

50% alcohol (optional) - for storing DNA.
You can use either isopropyl alcohol (rubbing alcohol) or ethyl alcohol for storing the DNA you extract. To make 100 ml of 50% alcohol with isopropyl alcohol, mix 71 ml of 70% isopropyl alcohol (rubbing alcohol) with 29 ml of distilled water. Using ethyl alcohol or Everclear grain alcohol, mix 53 ml of 95% ethyl alcohol (ethanol) with 47 ml of distilled water.

Paper towels
or filter paper - for drying DNA

Instructions

  1. Place 1 gram or 1 teaspoon of raw wheat germ in a 50 ml test tube, beaker or jar.

  2. Add 20 ml or 1 tablespoon of hot (50-60 °C) tap water and mix constantly for 3 minutes.

  3. Add 1 ml or a scant 1/4 teaspoon 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.

  5. Tilt the test tube, beaker or jar at an angle. SLOWLY pour 14 ml or 1 tablespoon of alcohol down the side so that it forms a layer on top of the water/wheat germ/detergent solution. Do not mix the two layers together. DNA precipitates 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 on top of the water solution. If the alcohol mixes with the water, it will become too dilute and the DNA will not precipitate.

  6. Let the test tube, beaker or jar sit for a few minutes. White, stringy, filmy DNA will begin to appear where the water and alcohol meet. You will usually see DNA precipitating from the solution at the water-alcohol interface as soon as you pour in the alcohol. If you let the preparation sit for 15 minutes or so, the DNA will float to the top of the alcohol.

    You can usually get more DNA to precipitate from the solution by using one of the DNA-collecting tools (such as a glass or paper clip hook) to gently lift the water solution up into the alcohol. This allows more DNA to come in contact with the alcohol and precipitate. You may find it helpful to pour the water/detergent solution into a clean test tube, leaving behind the wheat germ, before adding the alcohol.

  7. Use a glass or paper clip hook or a wooden stick to collect the DNA.

  8. If you want to keep the DNA, store it in 50 - 70% alcohol in a sealed tube or air dry it on paper towels or filter paper.
How does this work?

Here is the science behind this protocol.


Further experiments

Scientists often use a protocol, such as the instruction given in this activity, as a starting point for developing or improving techniques. Below are some ideas for things you might explore as you work to develop your own protocol.

DNA sources
Try using this protocol to extract DNA from other foods, such as oatmeal, seeds, yeast, etc.; the procedure may need to be modified (longer initial soak in hot water, etc.).

Detergents
Try using different detergents and soap products to extract DNA. Compare the amount of DNA extracted with these products. To quantify the amount of DNA you extract:

  • Weigh pieces of filter paper.
  • Use a hook to place the DNA you extract on these pre-weighed filter paper pieces. Spread the DNA out as much as possible; it will dry more slowly if it is clumped.
  • Let the DNA sit for several days until you are sure it is absolutely dry.
  • Weigh the filter paper again with the DNA.
  • Calculate the DNA weight:
    (Weight of filter paper + DNA) - (Weight of filter paper before DNA) = DNA weight.

Alcohols
Compare the amount of DNA obtained by using different alcohols. Use the procedure above (under Detergents) to measure the amount of DNA you extract.

Water temperature
Explore the effect of water temperature on DNA extraction by using different water temperatures with the protocol. Use the procedure above (under Detergents) to quantify the amount of DNA you extract.