The Questions of Developmental Biology

Why Clone Mammals?
Given that we already knew from amphibian studies in the 1960s that nuclei were
pluripotent, why clone mammals? Many of the reasons are medical and commercial, and there are
good reasons why these techniques were first developed by pharmaceutical companies rather than
at universities. Cloning is of interest to some developmental biologists who study the
relationships between the nucleus and cytoplasm during fertilization or who study aging (and the
loss of totipotency that appears to accompany it), but cloned mammals are of special interest to
those people concerned with protein pharmaceuticals. Protein drugs such as human insulin,
protease inhibitor, and clotting factors are difficult to manufacture. Due to immunological
rejection problems, the human proteins are usually much better tolerated by patients than proteins
from other animals. So the problem becomes how to obtain large amounts of the human protein.
One of the most efficient ways of producing these proteins is to insert the human genes encoding
them into the oocyte DNA of sheep, goats, or cows. Animals containing a gene from another
individual (often of a different species) a transgene are called transgenic animals. A
transgenic female sheep or cow might not only contain the gene for the human protein, but might
also be able to express the gene in her mammary tissue and thereby secrete the protein in her milk
(Figure 4.11; Prather 1991). Thus, shortly after the announcement of Dolly, the same laboratory
announced the birth of Polly (Schnieke et al. 1997). Polly was cloned from transgenic fetal sheep
fibroblasts that contained the gene for human clotting factor IX, a gene whose function is
deficient in hereditary hemophilia.
Producing transgenic sheep, cows, or goats is not an efficient undertaking. Only 20% of
the treated eggs survive the technique. Of these, only about 5% express the human gene. And of
those transgenic animals expressing the human gene, only half are female, and only a small
percentage of these actually secrete a high level of the protein into their milk. (And it often takes
years for them to first produce milk). Moreover, after several years of milk production, they die,
and their offspring are usually not as good at secreting the human protein as the originals.
Cloning would enable pharmaceutical companies to make numerous copies of such an "elite
transgenic animal," all of which should produce high yields of the human protein in their milk.
The medical importance of such a technology would be great, since such proteins could become
much cheaper for the patients who need them for survival. The economic incentives for cloning
are therefore enormous (Meade 1997).
Why Not Clone Humans?
Attorney John Robertson 1998a,John Robertson 1998b has listed several reasons why
cloning of humans should be legal. First, it would provide infertile couples with a chance to have
a genetically related child. The government, Robertson says, should not interfere with the ability
of any couple to have a genetically related child, and if cloning technologies are available, they
should be used toward that end. Second, cloning could provide a source of body parts for
transplantation (liver, pancreas, etc.) that would not be immunologically rejected. Third, in
Robertson's view, no harm would come to the individual or society. Fourth, the techniques for
cloning are not that different from other techniques of assisted reproduction, and the clone is
merely a "late-born twin."
In 1997, the Society for Developmental Biology, representing some of the developmental
biologists who pioneered cloning technology, argued against each of these positions and passed a
voluntary moratorium on human cloning for 5 years. This moratorium was subsequently adopted
by the Federation of Societies of Experimental Biology, and it has served as the basis for the