Build a Model of DNA Using Styrofoam Balls
Deoxyribonucleic Acid (DNA) is the genetic blueprint of the cell. It encodes all of the information for
cell to reproduce, make proteins, and function properly. The DNA molecuke winds like a spiral staircase
into a double helix. A sugar-phosphate backbone is forms the outside or "handrails" of the staircase.
A phosphate group consists of one phosphorus and four oxygen atoms. The phosphate group attaches to the
a carbon atom of deoxyribose to make up one block of "sugar-phosphate" that makes up the backbone.
This backbone of DNA repeats with every phosphate group attaching to the end of deoxyribose and forming
bonds with the end of the next deoxyribose molecule.
There are four nitrogenous bases that encode all genetic information in DNA: adenine (A), cytosine (C),
guanine (G), and thymine (T). The nitrogenous bases are on the inside of the structure and can be
considered the actual "stairs". The nitrogenous bases are ring structures formed of carbons, hydrogens,
nitrogens, and oxygens.
A nitrogenous base always attaches to the carbon of the deoxyribose molecule. The complete molecule of
sugar, phosphate, and nitrogenous base is called a nucleotide. A purine must always pair with a pyrimidine
to form the correct structure of DNA. Adenine always pairs with thymine while cytosine always pairs with
guanine. This is referred to as complementary base-pairing. Remember, there are two complementary strands
that make-up DNA.
Building a model of DNA is a great way to learn about how this magnificent structure builds our genes.
Gather Your Supplies
You'll need small styrofoam balls, a needle and thread, paint, and toothpicks.
Paint Your Styrofoam Balls
Choose six different colors to represent the sugar and phosphate groups, and the four nitrogenous bases.
They can be any six colors of your choice. You could choose to have one of the colors be white, so that
you don't have to paint some of the styrofoam.
You will need to paint 16 sugar balls, 14 phosphate balls, and 4 different colors for each of the nitrogenous
bases (cytosine, guanine, thymine, and adenine).
Pair Off the Nitrogenous Bases
Once the paint has dried, designate one color for each of the nitrogenous bases, and then pair them with
their matching base. Cytosine always goes with guanine, and thymine always goes with adenine. The order of
the colors does not matter, as long as they are in the correct pairs. Stick a toothpick between each of
the pairs, leaving a little extra space at the sharp ends of the toothpicks.