Arrange gumdrops into groups of four different colors. Create a legend on an index card to indicate the significance of each color. Represent the following four bases: adenine, thymine, guanine and cytosine.
Push a toothpick through two gumdrop pieces. Consult your legend to choose two pairing bases. Pair adenine with thymine and guanine with cytosine. Push a toothpick through two more gumdrop pieces, this time using the two colors not previously used that pair together.
Repeat the last step for all the remaining gumdrops, pairing all the colors, representing bases, together.
Arrange the toothpick pairings parallel to each other to resemble a ladder. Alternate pairings of adenin/thymine and guanin/cytosine for each rung of the ladder.
Align two licorice pieces on each side of the toothpick ladder. Push the licorice pieces into the toothpicks to connect all the rungs to the licorice, which represents the sugar phosphate backbone of the strands.
Pick up the structure, holding the licorice ends. Gently twist the licorice strands to resemble a twisted helix.