To discourage counterfeiters, signing of important documents with DNA is finding solid ground. Already a practice with American cartoonist Joe Barbara, who signs his creations with his own genetic material, the technique is the brain-child of Charles Butland of the Ios Angeles-based company, DNA Art Guard International (New Scientist, Vol 146, No 1971).

The genetic ink is prepared by isolating a DNA sequence from a source, sandwiching it between chemical primers, amplifying it through polymerase chain reaction and then mixing it with ordinary ink.