Caption

DNA. Computer model of part of a molecule of DNA (deoxyribonucleic acid). DNA is the molecule that controls the growth and development of all living things. Atoms are shown as balls, and are colour- coded: carbon (pink), oxygen (yellow), phosphorous (red), nitrogen (green) and hydrogen (white). The DNA molecule comprises two sugar-phosphate strands spiralling around each other (the double helix), linked by the interactions between pairs of bases along their length. The sequence of these bases along the DNA strands determines an organism's unique genetic code. Human DNA contains around 3 billion base pairs, grouped into sections (genes) controlling a specific function.