Attention-seeking amateurs have hijacked the cloning debate-and are eroding confidence in genuine researchby Robert A Weinberg / March 20, 2003 / Leave a comment
Biologists have been rather silent on the subject of human cloning. Some people accuse us of insensitivity to the consequences of our research. If not insensitivity, then moral obtuseness, and if not that, arrogance-an accusation that is never disprovable.
The truth is that most of us have remained quiet for quite another reason. Most of us regard reproductive cloning-a procedure used to produce an entire new organism from one cell of an adult-as a technology riddled with problems. Why should we waste time agonising about something that is far removed from practical utility and may forever remain so?
The nature and magnitude of the problems were suggested by Ian Wilmut’s initial report, six years ago, on his cloning of Dolly the sheep. Dolly represented one success amongst 277 attempts to produce a viable, healthy newborn. Most attempts at cloning other animal species-to date cloning has succeeded with sheep, mice, cattle, goats, cats and pigs-have not fared much better.
Even the successes come with problems. The placentas of cloned foetuses are often two or three times larger than normal. The offspring are usually larger than normal too. Several months after birth, one group of cloned mice weighed 72 per cent more than mice created by normal reproduction. In many species, cloned foetuses must be delivered by caesarean section because of their size. This abnormality, the reasons for which no one understands, is so common that it now has a name-large offspring syndrome. Dolly (who was normal at birth) was briefly overweight when young and suffers from early-onset arthritis of unknown cause. Two recent reports say that cloned mice suffer obesity and early death.
Arguably the most successful reproductive-cloning experiment was reported in November 2001 by Advanced Cell Technology (ACT), a small biotech company in Massachusetts. Working with cows, ACT produced 496 embryos by injecting nuclei from adult cells into eggs that had been stripped of their own nuclei. Implanting the embryos into the uteruses of cows led to 110 established pregnancies, 30 of which went to term. Five of the newborns died shortly after birth and a sixth died several months later. The 24 surviving calves developed into cows that were healthy by all criteria examined. But most, if not all, had enlarged placentas and, as newborns, some of them suffered from the respiratory distress typical of large offspring syndrome.
The success rate of the procedure, roughly 5 per cent,…