Bar coding objects with DNA

A bioanalytical scheme is described for bar coding objects with DNA. Several DNA templates of different lengths are mixed together and the mixture used to label the object of interest. To disclose the bar code, the DNA mixture is eluted from the object, amplified by the polymerase chain reaction with a universal pair of primers, and then the amplified templates resolved by agarose gel electrophoresis. In its present state, the bar coding scheme allows for over a million different labels. The reliability of the scheme has been demonstrated in a typical situation by labelling a letter with a template mixture (approximately 1.5 fmol of DNA), sending the letter through the post and successfully reading the bar code on receipt of the letter.