How was the sheep named Tracy genetically engineered?

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The sheep named Tracy was not created through cloning, but rather through genetic engineering techniques involving the direct injection of DNA into a sheep zygote (a one-celled embryo).1

Ian Wilmut and his team at the Roslin Institute developed a method to inject specific genetic material into the zygote pronucleus. This process was designed to enable the sheep to produce milk containing high levels of the human enzyme alpha-1 antitrypsin. This protein is medically significant as it is used in the treatment of cystic fibrosis and emphysema. This research was part of a broader effort known as "pharming," which aimed to use genetically modified animals to produce therapeutic human proteins.1