Illustration of a zinc-finger nuclease (pink) cleaving DNA (deoxyribonucleic acid, blue and white). Zinc-finger nucleases are artificial restriction enzymes, which are proteins that bind to and cleave specific segments of DNA or RNA (ribonucleic acid). They are based upon zinc-finger motifs: protein structures stabilised by one or more zinc ions (metallic spheres) that typically function to bind specific segments of DNA, RNA or protein. This makes them useful for gene editing technology as they can be engineered to recognise specific DNA sequences, which can then be targeted for gene insertion or removal. Atoms in the zinc-finger motifs are represented as rods and are colour-coded: carbon (grey), sulphur (yellow) and nitrogen (blue).