Smallness is a vestige of Molly’s tentative start in life. For a while Molly grew far too slowly, and the odds were good that she wouldn’t live much beyond the age of 6. She had been born with a rare disorder called Fanconi’s anemia, which was causing cells in her bone marrow–the ones that produce white blood cells and other defenses against infection–to fail. Molly needed new ones from a donor who was an almost exact genetic match. That meant that her parents needed to have another child, and fast. The trouble was, the odds of having one with the right genes and who didn’t himself have the disease were only one in four.
Fortunately for Molly, there was a way of loading the genetic dice. Mark Hughes, a molecular biologist, has worked for the past 10 years building and perfecting the genetic equivalent of a one-hour photo-developing shop. If parents want a child with certain genes, doctors first use techniques of in vitro fertilization to make dozens of embryos–however many it takes to ensure that one of them has the desired genes. Hughes’s technique, called preimplantation genetic diagnosis, then tells you which embryo to pick. What’s more, Hughes can perform the test in 24 hours, with time to spare for implanting the embryo into the womb. The Nashes used PGD to conceive Adam, now 2-1/2, who successfully donated umbilical-cord blood to save Molly’s life.
Molly wasn’t the first child to benefit indirectly from PGD, and she won’t be the last. While the world panics over false claims of human cloning, PGD is quietly transforming reproductive medicine by giving parents unprecedented control over what genes their offspring will have. So far the technique has been used largely, as in Molly’s case, in laudable efforts to avoid passing along single-gene inherited diseases. But PGD makes some people nervous, because it also gives doctors a rudimentary ability to manipulate traits–the morally reprehensible practice of eugenics. At present, manipulating complex traits like intelligence or athletic ability is impossible, but it may not always be. The fear is that as other aspects of reproductive technology improve, PGD may be misused. “There are 900 genetic tests available or in development,” says Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University in Baltimore, and a fellow of the World Economic Forum. “Determining which of these tests to offer to whom and at what point is really complex.”
Are the benefits worth the risk? Hughes, Molly’s parents and many others think so. PGD has in recent years moved into the mainstream of reproductive science. Clinics in London, Chicago, Tel Aviv and Brussels have recently begun to offer the procedure. Although Hughes doesn’t keep count, his personal computer lists dozens of obstetricians who’ve sent patients to his lab.
The process starts with the arrival of tiny plastic tubes packed in ice, each containing a single human stem cell plucked a few hours before from a three-day-old embryo. The cells come from fertility clinics, where would-be parents have their eggs harvested, fertilized and grown in petri dishes. By day three a human egg cell has managed to divide, on average, into only six stem cells. To find out if it carries the genes for Tay-Sachs or cystic fibrosis or sickle-cell anemia, the lab’s 60 researchers and technicians copy the sample cell’s DNA and analyze it with a Willy Wonka assortment of specialized machines. The trick is in coming up with clever ways of finding specific genes quickly, starting with only a single sample of DNA. Behind panes of glass, robotic hands shuffle trays of a hundred tiny test tubes.
The technique has attracted controversy in the United States simply because it involves embryos. In 1997 Hughes was accused of using federal funds for embryo work. He lost his funding from the National Institutes of Health and resigned from Georgetown University in Washington, D.C. (Hughes had initially taken up Molly Nash’s case, but was forced to abandon it. The Nashes eventually found a doctor in Chicago who performed the procedure.) Hughes moved to Detroit and set up the Center for Molecular Medicine and Genetics at Wayne State University.
The more substantial issue, though, is the specter of eugenics. At least one clinic in the United States is currently offering PGD services that allow parents to select the gender of their child, and more will surely follow. Hughes doesn’t condone the practice. “We won’t do gender selection,” he says. “Gender is not a disease.” What about fixing traits that make a good sibling donor? Are Hughes and other PGD specialists unwittingly turning children like Adam, selected to provide a transplant for his sister, into commodities? Hughes has struggled with this question and, he admits, has never managed to answer it unequivocally. He first confronted it when a case came up, before Molly Nash, while he was still working for the NIH in Washington. “I was very worried about it,” he says. “We had meetings. We published in a serious bioethics journal.” Hughes is not the kind of person who finds it easy to say no, and it’s not hard to imagine him taking pains to avoid the impatient parents. One day the husband tracked him down at his lab unannounced. “I’ll never forget what he told me,” says Hughes. “He says, ‘While you’re running around the world sitting at mahogany tables debating the bioethics of this, our daughter is dying.
" ‘People have children for all kinds of reasons’,” Hughes says, still paraphrasing. " ‘They have them for money, they have them for power, they have them to work on the farm. Mostly they have them by accident. What’s wrong with our having a child we’re going to love very much, but who also has the miraculous power to save our other child’s life?’" It’s not an easy question to answer.
