Reading DNA code

A gene is an instruction written in the language of the DNA code, which has four chemical letters (bases): A, C, T and G. Each A is always paired with a T, and each G always with a C. Scientists use a technique called DNA sequencing to reveal the order of these base pairs.

The inventor of DNA sequencing, double Nobel prize winner Fred Sanger (left), and a molecular geneticist reading a DNA sequence (right). The Nobel Foundation / Science & Society Picture Library