| Ian Wilmut, Keith Campbell, and Colin Tudge, The Second Creation: Dolly and the Age of Biological Control (Farrar, Straus and Giroux: New York, 2000). | |||||||||||||||||||
| Review by Tom W. Miller | |||||||||||||||||||
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In the first chapter, Ian Wilmut discusses the repercussions of the technology that created Dolly. Scientists are approaching the point where they will understand and control the processes of biological development. Wilmut concludes by opposing human cloning as risky and unnecessary. In the rest of the book, the authors do an excellent job of explaining the path that led to Dolly. Two themes dominate this story. First, science is a cumulative and collective activity. Second, Wilmut and company did not undertake cloning for the sake of replication, but to better understand cell differentiation and to create genetically engineered animals more efficiently. In 1990, scientists at Roslin and the biotech company PPL revealed their first triumph, Tracy the sheep. Scientists fitted Tracy with a human gene that caused the sheep to produce alpha-1-antitrypsin in her milk. AAT is an enzyme used to treat lung disorders like emphysema and cystic fibrosis. Tracy was a significant and enriching triumph, but the method that produced her was inefficient. The researchers had to work with zygotes--single-cell embryos created by the union of sperm and egg. Zygotes change quickly, are hard to work with, and are in limited supply. The scientists have to sprinkle the new DNA over the cells and hope that it attaches. Often, only some of the cells in the new organism incorporate the new DNA, resulting in what is called a chimera. Only after the chimera grows, breeds and passes the new gene to one of its offspring will an entirely transgenic animal result. Wilmut wanted to find a different way. If he could work with cultured cells, which he could multiply into the millions if he chose, he would solve the supply problem. He could then genetically transform the cells, create an embryo by nuclear transfer, and immediately produce a transgenic animal without having to wait a generation. Wiilmut knew of Steed Willadsen's successes in creating organisms with embryonic sheep cells and nuclear transfer. Wilmut borrowed much of Willadsen's technique and sought to build on his work. At what point did cell become so specialized that it could not be induced to create an entirely new organism? Wilmut began to suspect that the cell cycle--the process of cell growth and division--had something to do with the matter. Enter Keith Campbell, cell cycle expert. Campbell suggested that nuclear transfer would be more likely to succeed if the deed was done before the chromosomes began to replicate. In an experiment that led to Megan and Morag, the first lambs created with cultured, unquestionably differentiated cells, Campbell first deprived the cells of growth factor to induce a quiescent state known as G0. This was the easiest way Campbell knew of to ensure that the chromosomes had not yet started to divide. After the success of this experiment, Campbell had an epiphany. Maybe G0 is not just a convenience, but crucial to the process of reprogramming a cell. Campbell wanted to test his theory by trying to clone from an adult cell. Working with the mammary cell of a six-year-old ewe, the Roslin team confirmed Campbell's hypothesis by creating Dolly. A year later, the birth of Polly fulfilled Wilmut's original dream. The team cloned Polly from a differentiated fetal cell fitted with a gene for human factor IX. The scientists had bypassed the chimera stage and immediately created a fully transgenic animal. The Roslin story, though at times laden with difficult jargon, is a splendid case study of how a scientific breakthrough occurs. The authors conclude by pondering the possible ramifications of their achievement. Wilmut and Campbell suggest several positive applications of cloning technology. Scientists could create purebred strains of mice for the laboratory without resorting to inbreeding that inherently weakened the strain. The livestock industry could clone elite animals to increase herd productivity. Conservationists could use cloning to help preserve endangered species. In the medical field, scientists could clone human tissue to repair burned skin, damaged organs, and neurological dieseases. However, both Wilmut and Campbell oppose reproductive human cloning. The process would simply involve too much physical risk for the embryos and children that resulted. Besides, there is no need for human cloning. Infertile couples have other, safer means available to produce the healthy children they want to love. The first point is well taken. Even most people who support human cloning would not want to see it happen until researchers can minimize the risk of physical deformity. The second point, though, downplays the influence of an important human drive: the desire to have a genetically related child. With some infertile couples, cloning would be the only way to achieve this result. Wilmut and Campbell may have ushered in the age of biological control, but society has yet to answer whether and how it will control this new, powerful knowledge. |
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