Remote-control molecular factory

Engineered bacterial cells can churn out medically useful proteins such as insulin, the blood-clotting agent thrombin, and a host of other human enzymes and hormones. Plants, yeast and even other mammals can be given the genes needed to produce valuable proteins that they don’t make naturally. Most famously, even notoriously, genetically modified goats can secrete spider silk in their milk, which can be extracted and used to make tough fibres.