DNA (deoxyribose nucleic acid) is life’s genetic code that tells the body how to function or what to look like. The DNA code is made up of 4 different chemical units called bases. The bases are adenine (A), thymine (T), guanine (G) and cytosine (C). The code, if you were to read it, would look something like this:

...CGTAGCTTACTTTAGGCTAGCAAACGCATC....

A gene is a section of genetic code that can be decoded by the cell to mean something. A single gene might be responsible for any aspect of your body's function or appearance, like making a certain protein, or the colour of your eyes.

If there is an error in the code for a gene the product will be faulty, see Genetic mistakes. The DNA (genetic code) is packaged into chromosomes inside each cell, see What are chromosomes.