Double Helix DNA Candy Model

 source  No. 5

This tasty science project is super simple to do in a home lab and is extremely effective in teaching students about DNA, base pairs, and the double helix structure of human DNA. We recommend completing this project with 4th, 5th, or 6th-grade students because it requires the ability to carefully follow directions, work semi-independently, and use fine motor skills.

The Science Connection

DNA, or Deoxyribonucleic Acid, contains the instructions for how all cells in all living creatures—including your students—grow and develop. DNA contains genes, which have information for how to make proteins. Without DNA, there wouldn’t be any humans.

DNA is instantly recognizable by its form, which is a double helix. DNA is composed of two backbones (or the long straight parts on either side of a ladder) and base pairs (the rungs on the ladder). This project helps develop an understanding of the structure of DNA, and helps students remember the four base pairs of DNA: Adenine, Thymine, Cytosine, and Guanine, as well as which base pairs with which.

Materials and Instructions

Materials Needed 

• 2 pieces of licorice
• 17 toothpicks
• Small marshmallows in 4 colors (9 of each color). Small gumdrops can also be used if you can’t find marshmallows in multiple colors.
• Masking tape
• 
  

Instructions 

• Choose a DNA sequence to make a model of (suggested sequences are Sequence 1: TACGTATGAAAC and Sequence 2: TGGTTTAGAATT).
• Assign a marshmallow color to each chemical base in DNA (suggested color codes are (A) Adenine = green marshmallow, (T) Thymine = pink marshmallow, (C) Cytosine = yellow marshmallow, and (G) Guanine = orange marshmallow).
• Assemble the first half of your DNA by pushing a small marshmallow onto one side of a toothpick (be sure to use the appropriate color to represent the appropriate base) and then poke the same side of the toothpick into your piece of licorice. When this is complete, you should have licorice with a line of marshmallows along it and empty toothpick ends.
• Match your DNA bases by putting another marshmallow on the other side of the toothpick, and then attaching the ends of the toothpick to the other licorice string. Remember, only certain bases pair with other bases. A always pairs with T, and C always pairs with G.
• Using your remaining toothpicks and masking tape, label your model.
• Twist your model so it takes on the appropriate double helix shape.

Tip 

For a slightly healthier edible double helix, you can choose to use fruit or veggie chunks for your bases (grapes and cherry tomatoes work well) and small pretzel sticks instead of toothpicks. Unfortunately, because the backbones have to be flexible, licorice is still the best choice for them.