Genetic code. Conceptual computer artwork of the individuality of DNA showing a hand overlaid with a DNA molecule, letters forming the genetic code, a bar code and chromosomes. Each individual has a slightly different genetic code, made up of the sequence of four bases in DNA (deoxyribonucleic acid). These are adenine (A), thymine (T), guanine (G) and cytosine (C), which can be represented by their letter code or colours (as seen). DNA is found in all living things and controls growth and development. Chromosomes are thread-like strands of DNA, which carry the genetic code. Bar codes (down right) are able to encode information in the form of black bars.