How to Make a Double Helix DNA Model

DNA molecules are the essential building blocks of life. They are also the keys to understanding other functions of molecular biology. Making a DNA molecule for an elementary or middle school science fair project is often an arduous task for students and a headache for parents. Constructing a detailed but inexpensive DNA molecule can be accomplished in under three hours with a minimal amount of help from parents or older siblings and a single trip to a drugstore.

Things You'll Need

• Bag of red licorice
• Bag of black licorice
• Bag of clothespins
• Orange marker pen
• Green marker pen
• Purple marker pen
• Blue marker pen
• Transparent packing tape

Instructions

1. Use the orange pen and write a capital letter "A" on both sides of where you squeeze the clothespin. Write the letter perpendicularly on the clothespin. Write a perpendicular "A" on three of your clothespins. Repeat this step for the remaining colors using the following key: Green G (for guanine), purple T (for thymine), blue C (for cytosine) and orange A (for adenine).

2. Take two black licorice sticks and gently stretch them---being careful not to break them. Once they are stretched a bit, lay them end-to-end. Connect them at the bottom with a clothespin labeled "A."

3. Continue building the phosphate base by connecting another stretched black licorice stick to the bottom of the two you just built using a "G" clothespin. Add another stretched licorice stick using a "C" clothespin. Add your fifth licorice stick using a "T" clothespin. Place another "T" clothespin at the top of your black licorice tree to complete your phosphate base.

4. Now repeat the process with the red licorice sticks except on the red side, you are going to connect your first two licorice sticks with a "T" clothespin. The next clothespin connection will be a "C" clothespin followed by a "G" clothespin and your fifth clothespin for the red chain will be an "A" clothespin. Place another "A" clothespin at the top of the red licorice tree. This completes your sugar base.

5. Finally, gently overlap the red and black licorice sticks and use transparent tape to connect the handles of the clothespins, making sure you can read the letters on both clothespins. The overlap is necessary to produce the defining double helix characteristic of DNA. Adjust the clothespin positions as necessary to tape the handles together. Make sure that only the "T" and "A" clothespins are taped together and that only the "C" and "G" clothespins are taped together. Gently twist the model to create the helix shape.

Tips & Warnings

• Some students find it easier to tape the clothespins first and then attach them to the red and black licorice sticks.

• You may want to coat the ends of the clothespins white before you write letters on them.

• Remember to always pair "A"s with "T"s and "C"s with "G"s.