If you have any questions regarding these projects, go to www.scifair.org and click on the Real Simple link.

Project No. 1: Extract DNA in Your Kitchen

DNA is the largest known molecule and the foundation of all life on earth. It’s also surprisingly easy to extract from living things and experiment with at home. All you need to do is pick your DNA source (say, a fruit or a vegetable), break open the cells, and soak them in a solution called a “buffer” so the molecular guts can leach out. Then you simply strain out the guts, add a little alcohol, and — presto! — stringy clumps of DNA will appear.

What You Need

About 6 ounces distilled or bottled water

Small glass or metal mixing bowl

1/4 teaspoon table salt

1 teaspoon baking soda

1 teaspoon liquid detergent (Not soap. Use laundry detergent, dish detergent, or shampoo. Look for the words sodium lauryl sulfate on the label.)

Crushed ice (to chill the solution)

Source of DNA (a fruit, a vegetable, a type of fungi, a legume, or even a piece of meat)

Drinking glass

Old nylon stocking

Small, narrow glass container, preferably with straight walls (A test tube is ideal, but other kinds of small glasses will work.)

Isopropyl, or rubbing, alcohol with no additives (Chill the bottle in the freezer before you begin.)

Drinking straw

Ruler, preferably with a centimeter scale

Glass swizzle stick (If you don’t have one, you can use a cotton swab.)

What You Do
Step 1: Make the buffer.
Pour the distilled or bottled water into the mixing bowl. Dump in the salt and stir until dissolved. Add the baking soda and stir until dissolved. Pour in the liquid detergent and stir. Chill the buffer solution in a bath of crushed ice and water. (DNA degrades fast — in a matter of minutes in some circumstances. This will help slow the rate of destruction.)

Step 2: Add the DNA to the buffer.
For a DNA source, try the pantry. I always get great results with an onion. But garlic, bananas, and tomatoes work well, too. Once you’ve secured your DNA source, you’ll need to process its cells to get out the DNA. Here’s how.

Dice the DNA source with a kitchen knife. Put the diced material into a blender or a food processor. Pour in just enough distilled or bottled water to cover the material. Break up (or lyse) the cells by blending the material into a slushy mass. Place 1 teaspoon of the slushy mass into the drinking glass. Mix in 2 teaspoons of the chilled buffer. Stir gently for at least 2 minutes. The “guts” of the broken cells will leach out into the buffer.

Step 3: Remove the bulk matter.
Strain the mixture through the toe of an old nylon stocking. Discard the bulk matter and pour the resulting DNA solution into the test tube (or a narrow glass container).

Step 4: Extract the DNA.
Now you’re ready to extract the DNA so you can measure and collect it. Here’s how. Get the bottle of isopropyl alcohol from the freezer. Using a drinking straw, carefully deposit chilled alcohol on top of the DNA solution (because the alcohol is less dense than the buffer, the alcohol will float on top). Dip the straw into the bottle of alcohol, pinch the top of the straw, and transfer the alcohol to the test tube, tilting the tube slightly and allowing the alcohol to slowly stream down the tube’s inside wall. Repeat this process until you have a thick layer (about 1 to 2 inches) of alcohol sitting on top of the DNA-laden buffer.

Where the two liquids meet, you should see a gelatinous sludge, in which tiny, sinuous tendrils have magically started to appear. That sludge is DNA!

It’s easy to find out how much DNA you’ve extracted. Just stand a ruler along the side of the glass to measure the thickness of the DNA. If you use this same container to extract DNA samples from a number of different materials, you’ll be able to compare relative yields of DNA. To remove the DNA, insert the glass swizzle stick into the DNA layer and slowly twirl it continuously in the same direction. The sticky strings of DNA will wind up onto the stick like spaghetti on a dinner fork. If you like, you can then redissolve your DNA catch in a fresh batch of buffer (no need for the detergent this time) and expose the DNA in the new buffer to heat or chemicals to determine what conditions cause DNA to break apart.