Fruit-fly DNA Tagged Bank Notes

Recently, the new £5 note issued by the bank of England was found to have been manufactured using animal parts, specifically a tiny amount of beef tallow. Now, the Vegan population responded in the usual level-headed and proportionate manner by being outraged at the presence of near-homeopathic quantities of byproduct bovine triglyceride. This situation has now been rectified to the satisfaction of all, the notes are now cow-free and the Vegans can talk about this at parties for a decade or so.

While I'm enthusiastic about the general principle of making money a meat product, I think they went the wrong way with cow fat. You don't really get any added features. DNA is a lot more useful. DNA sequencing is cheaper than it used to be. A whole genome sequence used to be announced by a president with great fanfare, now it's announced by email, with coffee. If you could get DNA into your banknote, you could use it as an embedded anti- fraud mechanism, tying a specific sequence to the serial number. Now, you COULD just synthesize a little DNA molecule encoding just the information you need plus a couple of convenient primer sites and mix that in with the note as it is made. The trouble there is that you have to synthesize a unique molecule for each note and the DNA is going to be small. This means any old common criminal with a garden-variety molecular biology lab can forge your banknotes.

Much better to let nature do the DNA production and variation. Simply grow a series of varied Drosophila fruit fly colonies, and smash one fly into each individual banknote during production. Then, should you want to trace the production, you sequence the DNA and you can use all the phylogeny and other tedious genetic analysis to establish when and where the note was made. The producer should also keep a small section of the note for exact matching, but regular sequencing of the fly colonies every 10 generations or so should get you in the ballpark.

For the foreseeable future, criminal currency forger aren't going to be able to synthesize whole genomes, and you Vegan-proof your money. Extra points for growing the files on the various stable phosphorous isotopes.