7 The 100 Most Influential Inventors of All Time 7renamed Edinburgh Research Station of the Institute of
Animal Physiology and Genetics Research in 1985 and
finally Roslin Institute in 1993), a government-supported
research facility located in Roslin, Scot., just south of
Edinburgh. At the ABRO facility, Wilmut studied embryo
development and became interested in the underlying
causes of embryo death in mammals. However, in the early
1980s, changes in ABRO leadership and a shift in the focus
of government research projects forced Wilmut into the
realm of genetic engineering. The new goal of ABRO was
to generate sheep genetically engineered to produce large
quantities of human proteins that would be suitable for
therapeutic uses, a pursuit that came to be known as
“pharming.” Although Wilmut had little experience with
genetic engineering and had limited enthusiasm for the
project, he used his knowledge of developmental biology
to obtain zygotes (one-celled embryos) from sheep and
developed techniques to inject DNA into the zygote pro-
nucleus (a haploid nucleus occurring in embryos prior to
fertilization). This work eventually led to the generation
of a sheep named Tracy. Tracy was created from a zygote
genetically engineered through DNA injection to produce
milk containing large quantities of the human enzyme
alpha-1 antitrypsin, a substance used to treat cystic fibrosis
and emphysema.
Nuclear Transfer
Wilmut’s initial forays into cloning began in the late 1980s
with embryonic stem cells. Wilmut and his colleagues
were interested primarily in nuclear transfer, a technique
first conceived in 1928 by German embryologist Hans
Spemann. Nuclear transfer involves the introduction of
the nucleus from a cell into an enucleated egg cell (an
egg cell that has had its own nucleus removed). This can