One of the most productive research partnerships in the recent history of science began on a warm Caribbean evening in 2011.

Emmanuelle Charpentier, a French microbiologist then working in Sweden at Umea University, and Jennifer Doudna, an American biochemist at the University of California, Berkeley, had just met for the first time at a conference in Puerto Rico. Walking around the old town of San Juan, they discussed the way bacteria defend themselves against infection, by targeting and chopping up the DNA of attacking viruses.

This aspect of the bacterial immune system — a combination of genes and enzymes known as Crispr (short for clustered regularly interspaced short palindromic repeats) — had been an obscure curiosity in microbiology. But Profs Charpentier and Doudna saw how it might be transformed into powerful molecular scissors to cut and edit genes in any living creature.