This stuff, your DNA, contains the instructions to make your body (look at student's tubes of DNA)
(There is also some protein mixed in. The long strands you see are the DNA molecules. The protein sticks to these strands and makes them a little whiter than pure DNA.)
The instructions are made up of just 4 units, that we call A, C, G and T.
We each have 3 billion units in our DNA, just made up of those 4 letters.
In each of us, these units are linked together in a different order. That means our instructions for making our bodies are different from each other – so we all look different.
(Identical twins have the exact same order of units, so their instructions are exactly the same - that is why they look the same.)
You will hang your DNA on a string, that you can make into a necklace or bracelet if you like, with the 4 letters of the code.
Pick out one each of the 4 DNA units, one each of A, C, G and T and thread them on the string.
Carefully open up your tube of DNA loop the cap around the string and close it again tight.
If students are making the code on their necklace to spell out their name, explain how every 3 DNA letters make a protein unit. They will use the protein unit letters to spell out their name (see attachments).