Materials needed:

One empty cardboard paper towel roll
Two different colors of construction paper
Scissors
Magic marker
Glue
 

Procedure:

We are going to make a DNA strand.

On the paper towel roll, locate the line which spirals up the roll, where the was joined together at the factory.  Using scissors, cut along this line from one end of the roll to the other.  When you finish, you should have a piece of cardboard the shape of a spiral.   If you were to flatten out the spiral, it would look like this:

Choose two different colors of construction paper, say yellow and green.  Cut some little strips of construction paper about 1/2 inch wide out of both colors.  These are going to be the rungs of the ladder which makes up the twisted strand of DNA.  Each child will glue the colored strips on the piece of cardboard in approximately this fashion:
 
 

However, in an actual strand of DNA, each rung of the ladder is not one piece, but two small pieces connected at the center, like this:
 
 

So, you can either have the strips already cut out ahead of time in these shapes for the children to label and glue on, or you can let them cut out the strips themselves, depending upon their attention span and the amount of time you have to complete the craft.

The rungs on the ladder of DNA are made from amino acids.  The letters on the rungs correspond to the following amino acids:

A = Adenine    T = Thymine    C = Cytosine    G = Guanine

Adenine and Thymine always pair together, and Cytosine and Guanine always pair together.  These pairs never mix up, so you would never have a Thymine with a Cytosine.  However, in the drawing above, you will notice that while the position of the pair vertically is always the same, horizontally the members of the pair do switch back and forth.  So the first time you have an AT pair, the A will be on the left, and the next time you have an AT pair, the T will be on the left.

I would have the children glue the strips of paper on first to make sure they get the alternating colors, THEN have them label the strips.  Labeling them first and then pasting them on would be too confusing.

After the strips are glued on, and labeled with a letter, the children should draw in the dotted lines between the pairs which represent the hydrogen bonds.  AT pairs have a double bond, and CG pairs have a triple bond.

By way of explanation, A, T, C, and G are Amino Acids.  Amino Acids are the building blocks of protein.  They are the ingredients that are used to make protein.  When making a cake, you have the same basic ingredients no matter what kind of cake you are making.  But for one, you put in chocolate and for another you put in vanilla, and for another you put in lemon.  You use different combinations of amino acids to make different kinds of protein, just like you add different flavorings to make different kinds of cakes.  There are 21 different amino acids in all, so you can see that many different kinds of proteins can be made.  DNA just happens to use these four.

After all this is explained, and the stripes are glued on and the bonds connect them, you should have a spiral-shaped ladder with colored rungs.  You can then attach a string to the top of the spiral and hang if from the ceiling.

Click Here to see two different illustrations of the DNA molecule.

Remembering our discussion on the previous page about the creation of life, DNA requires protein to make the rungs of the spiral ladder.   So where does the DNA molecule get the protein to make the rungs?  It has to be manufactured, and the instructions for manufacturing the protein are in the DNA!  So you see, neither the DNA or the protein could have existed before the other one, they both had to be created at the same time so they could both be available at the same time.

Some scientists try to say that one existed and developed into the other one, but this could not be possible.  An intelligent being or force KNEW that both needed to exist at the same time, and made them both available.