PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY
Transgenic sheep. Sheep with a human gene in their DNA. The gene is responsible for the production of the protein alpha-1-antitrypsin (AAT). Hereditary deficiency of AAT in humans leads to emphysema, and affects about 100,000 people in the western world. Copies of the gene are injected into a newly-fertilised sheep's ovum, and may become incorporated into the sheep's own DNA. In mammary cells, the gene activates AAT production in the sheep's milk. The AAT isolated from the milk for use in therapy. Clinical trials are due to start in 1995. Photographed at Pharmaceutical Proteins Ltd, near Edinburgh, Scotland.
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