How to Create a 3-D Model of DNA
DNA (deoxyribonucleic acid) is the basis of genetic inheritance. Although variability in this molecule gives rise to all biodiversity, its basic structure is simple. DNA has a characteristic double helix structure, with pentose sugar and phosphate molecules forming the outer framework. Pairs composed of four bases--either adenine and thymine or guanine and cytosine--link the molecule together. The exact sequence of bases determines the specific genetic information. Making a DNA model helps students understand the structure and patterns of this important biological molecule.
Other People Are Reading
Things You'll Need
- 72 Small styrofoam balls
- Red and black pipe cleaners
- Scissors
- Glue
- 6 colors of poster paint
- Small paintbrush
Instructions
-
-
1
Choose the colors for the six different molecules: pentose sugar, phosphate, adenine, thymine, guanine, and cytosine. Paint 24 balls with one color to represent the sugar molecules. Paint an additional 24 balls in a different color to represent the phosphate molecules. Paint six balls each for the four different bases.
-
2
Cut black pipe cleaners into short (1- to 2-inch) lengths for a total of 48 pieces. Dab a small amount of glue onto the ends of a piece of pipe cleaner, then poke one end into a ball representing sugar and the other end into a phosphate ball. Connect the phosphate to a new sugar molecule, using an additional pipe cleaner piece and glue. Repeat to make a string of alternating sugar and phosphate balls. Make two strands with 24 balls in each.
-
-
3
Cut red pipe cleaners into short (1- to 2-inch) lengths for a total of 36 pieces. Put a small amount of glue on each pipe cleaner end, then pierce base molecules with pipe cleaners. Make sure to pair adenine with thymine and cytosine with guanine for a total of 12 pairs.
-
4
Lay the two sugar-phosphate strands (created in Step 1) a few inches apart on a flat surface. Take an adenine-thymine pair and connect it to both strands with two pieces of red pipe cleaner and glue. Repeat this process with a cytosine-guanine pair.
-
5
Gently twist the sugar-phosphate strands in opposite directions to start creating a double helix. Continue connecting base pairs, until all the balls have been used. Make sure to place the pipe cleaner into each ball at an angle that allows the strands to curve.
-
6
Let the model dry thoroughly before mounting either on a support stand or suspending from a string.
-
1
Tips & Warnings
To make a more rigid DNA model, use large wooden beads joined by wire. An edible version uses colored mini marshmallows or gum drops and licorice. Consider how to display the model. Construct a simple stand using a wooden dowel placed into a shoe box.
Foam balls will slip off the pipe cleaners without glue. If all the balls are connected before the strands are twisted, it will be impossible to form a double helix shape.
