Free Frankenstein's Cat: Cuddling Up to Biotech's Brave New Beasts by Emily Anthes Page A

transfer don’t divide properly, some fail to nestle into the warm and welcoming uterine wall, some spontaneously abort themselves. In creating Dolly, for instance, the Roslin Institute researchers had made 277 attempts to make cloned embryos and ended up with just 29 viable ones. They were all transferred to surrogate mothers, and as time passed, the numbers dwindled further, until only one cloned fetus was left—the lamb that would be Dolly.
    The challenges associated with cloning go beyond low success rates. Dolly died at age six, well short of a sheep’s normal life expectancy. The lamb’s creators maintain that her demise had nothing to do with cloning, pointing out that four other sheep in the barn also came down with the same contagious lung disease that took Dolly’s life, but scientists are still plagued by questions about the health of cloned animals.
    It’s impossible to draw definitive conclusions about Dolly—or any other single case—but since her death, biotech companies have cloned hundreds of farm animals, and we’ve amassed much more data on the health of clones. The evidence is troubling. Failures and defects are a normal part of reproduction—not every fertilized egg implants in the uterine wall, and stillbirths and birth defects can happen no matter how an animal comes into being—and assisted reproductive technologies, such as in vitro fertilization, increase the risk of certain abnormalities. But clones, at least in some species, are more likely to suffer from birth defects and health problems than animals made by other means.
    That’s what the FDA concluded in a nearly thousand-page report, published in 2008, on the health of livestock clones. While the agency found no evidence of unusual health problems in cloned goats or pigs, it reported that cloned cattle and sheep do have an elevated risk of abnormalities. In particular, the animals are at risk for “large offspring syndrome,” which can cause respiratory and organ problems in the newborns and complications for their surrogate moms. Cloned cows and sheep are more likely to die in the womb or shortly after birth than their conventionally conceived counterparts. However, the data reviewed by the FDA also showed that if the youngsters can be safely shepherded through the first six months of life, they seemed to develop into perfectly healthy adults, and when these clones reproduce the old-fashioned way, their offspring appeared to be normal. That said, the FDA also noted that “it is not possible to draw any conclusions regarding the longevity of livestock clones or possible long-term health consequences associated with cloning due to the relatively short time that the technology has existed.”
    Scientists believe that many of the poor outcomes seen in cloning can be traced back to a process known as genetic reprogramming. When a sperm cell fertilizes an egg, it initiates a cascade of changes. Some genes get turned on, while others are switched off, as the embryo grows and divides. Throughout the course of development, various genes are constantly being amplified or silenced, particularly as cells become specialized, or “differentiated.” The activation or expression of certain genes equips a cell to join the heart, for example; the expression of different genes turns a cell into part of the skin, or the blood, or the brain instead.
    For years, scientists thought cellular differentiation was irreversible—once a skin cell, always a skin cell. Dolly’s birth smashed that assumption. Through the process of nuclear transfer, the scientists had managed to take the DNA from a differentiated mammary cell and turn it into something that a developing embryo could use. Cloning other adult mammals reinforced the discovery that nuclear transfer can reset genes contained in specialized cells back to their embryonic state. It was an astonishing accomplishment, turning back the genetic clock, but this process may not always go perfectly. As