|This diagram show how Dolly the sheep was|
made. A similar approach was used to make
In order to create Polly, scientists used sheep fibroblasts into which a transgene was inserted that was designed to express the protein human clotting factor IX in the milk of the sheep. These fibroblasts then underwent the same nuclear transfer that allowed for the cloning of Dolly. The goal was to demonstrate the potential of recombinant DNA technology and cloning to produce therapeutic proteins that could be used to treat human disease. Clotting factor IX was chosen due to its essential role in coagulation and use in treatment of hemophilia B.