Your DNA is like your thumbprint. It is yours and yours alone. Unless you have an identical twin, no one else on the planet has exactly the same DNA as you.

In the nucleus of almost every cell in your body is the collection of DNA needed to make you. DNA in the nucleus is grouped into 23 sets of chromosomes that are called your "genome." In each chromosome, the DNA is grouped into "genes." Your genome contains about 35,000 genes. Each gene carries information that tells the cell to make a unique protein that will perform a special function.

How does something so small contain all of the instructions to make your whole body and keep it working? That is answered in the chemical makeup of DNA. If you think of your genome (all of your chromosomes) as the book that makes you, then the genes are the words that make up the story. They do that by making proteins, which do most of the real work in the body. The DNA in your genes tells the cell what amino acids (protein building blocks) to put together to make a protein. The letters that make up the words are called DNA bases, and there are only four of them: adenine(A), guanine(G), cytosine(C), and thymine(T). It's hard to believe that an alphabet with only four letters can make something as wonderful and complex as a person!