This summer, Scotland’s Roslin Institute, the birthplace of Dolly the sheep, announced its newest brood: genetically modified hens that lay eggs laced with anticancer drugs. The eggs are the latest creation of animal biopharming, a nascent field that aims to turn critters into low-cost substitutes for pharmaceutical factories. Borrowing a technique used in human gene therapy, researcher Helen Sang and her team coaxed a virus to transport an altered gene into the DNA of hens, which later expressed a protein in their eggs’ whites that fights melanoma. In the future, the drug will be extracted in a lab and then turned into medication. If all goes well, the process could slash manufacturing costs by up to 99 percent.