Sarah Montague speaks to biochemist Jennifer Doudna. Crispr Cas9 has been described as the greatest biological breakthrough in decades. It is a gene editing tool and the hopes that rest on it are immense - that it can be used to cure cancer and other intractable diseases, stop mosquitoes carrying malaria, create drought resistant crops and food that does not rot, even that it can recreate extinct animals. What does she make of the breathtaking pace of innovation since her discovery and does she fear where it may lead?