Dolly, a sheep unremarkable
except for her origin, has caused us to stop and think.
Dolly, as the world knows, is the sheep cloned at Scotland's
Since the formal announcement of her existence, there has been an intense
public debate over the ethics of cloning both animals and humans. What hasn't
been heard is the thinking behind Dolly's creation.
The scientists at Roslin Institute have conducted research for many years to
produce rare drugs in the milk of sheep and cattle. That research was sparked
by a U.S. Department of Agriculture study
that showed new genes, including human genes, could be inserted into sheep,
pigs, and rabbits.
Some dozen years after this USDA study, the research at Roslin has begun to
pay off. The Roslin scientists introduced into sheep a modified human gene that
promotes production of the human protein alpha-1 antitrypsin.
The Roslin scientists found that the human gene functioned in sheep and
caused alpha-1 antitrypsin to be produced in the sheep's milk. The Scottish
biotechnology company PPL Therapeutics has purified the human protein from the
sheep milk and is testing it as a drug for the treatment of emphysema.
After seeing the power of this technology for alleviating human pain and
suffering, many researchers sought support to conduct similar research on genes
that produce other rare human proteins. Scientific reports indicate that human
proteins for several blood clotting factors and for one antibacterial protein
have been produced in animals' milk.
USDA's investment in research to understand genes and how they work appears
to have produced an early payoff in biomedicine.
Dolly represents a new approach to inserting genetic information into
animals. How does this new approach improve on the method reported by USDA?
In the earlier method, genes were injected into eggs. But the success rate
was low. Less than one out of a hundred eggs would ultimately produce an adult
animal with the inserted gene. Meanwhile, the investment in surrogate mothers
for the 99 eggs that didn't carry the new gene made the research expensive.
In contrast, Dolly was produced from cells grown in the laboratory. In
theory, if a new gene had been added to those cells, then all of Dolly's cells
would have carried the new gene. Experiments are under way to test this
Returning to the issue of the benefits of cloningwill we produce much
of our lean meat from clones? It seems unlikely, at least for a while.
Producing Dolly was expensive and inefficient.
Also, we must protect the genetic diversity of our food-producing animals so
they can respond effectively to challenges such as emerging diseases or
climatic change. If all animals were genetically identical, they would all have
the same vulnerabilities.
It is possible that with appropriate germplasm conservation programs, we can
design farm management programs to maximize the consistent qualities of a set
We in USDA's Agricultural Research
Service expect to put the methods that produced Dolly to a variety of uses.
For example, they might help us learn more about the genes behind whether an
animal uses food to make muscle or fat and about the genes that control a cow's
level of resistance to mammary gland infections. They will aid the study of
methods to make milk an even healthier food for peopleespecially
infantsand there will be other studies that we have yet to envision.
Just as the basic research at USDA was the predecessor to Dolly, the new
research made possible by Dolly will ultimately pay off in many ways, for
animals and people alike.
Caird E. Rexroad,
Research Leader, ARS
Gene Evaluation and Mapping Laboratory, Beltsville, Maryland
"The Promise of Dolly" was published in the May 1997 issue of Agricultural Research magazine