Well, Goodbye Dolly

1996�2003

From the beginning, interest in Dolly was more moral than scientific.

When Ian Wilmut, a scientist at the Roslin Institute in Scotland, removed the nucleus from an udder cell of one sheep and injected it into a ewe�s egg cell from which the DNA had been removed, he proved that adult DNA could be reset to create a new organism. Dolly, the first cloned mammal, was born on July 5th, 1996—the last of 277 attempts by Dr. Wilmut to create a cloned sheep.

Dolly (whose origin as an udder cell suggested her namesake, country singer Dolly Parton) immediately became emblematic of the debate over human reproductive cloning. For many, like the bioethicist Leon Kass, there was something insuperably repugnant about cloning. Others fretted that people would want clones for selfish reasons—because they hoped for a kind of personal immortality or to resurrect a dead child. Defenders of human cloning, like Dr. Wilmut himself, acclaimed that Dolly was “the most extraordinary creature ever to be born.”¹ Hostage to both parties, poor Dolly became the cover girl for a hundred overheated editorials.

But for those without ideological fixations, the debate centered on the welfare of the clone itself. Was cloning safe? When Dolly was put down on February 14th, the answer seemed to be, We don�t know, but it doesn�t look good.

Sheep of Dolly�s breed, the Finn Dorset, often live for ten years or more. But an autopsy revealed that Dolly had sheep pulmonary adenomatosis, a virus-induced cancer, and arthritis, ailments common to older sheep. The autopsy revived earlier worries about Dolly�s health: in 1999, it was discovered that her telomeres were 20% shorter than normal for her age. This led some scientists to suspect that Dolly�s real age was hers and her mother�s combined.

A telomere is a repeated sequence of five base pairs that preserves the integrity of genes during DNA replication: each time a cell replicates, its daughter cells have slightly shorter telomeres than those of the parent. Telomeres eventually become so short that the DNA strands either stop replicating or begin to fuse, encouraging tumors to grow. It�s not clear whether short telomeres actually cause age-related diseases, or whether they are a symptom of some other aging mechanism. Richard Cawthon, a geneticist at the University of Utah, has measured the telomeres in people age 60 and older (see “Twist of Fates,” page 76 of the Journal, Issue 1). Those with shorter telomeres were eight times more likely to die from infectious diseases (like Dolly�s lung ailment) and three times more likely to suffer a fatal heart attack.

Earlier studies of cloned mice demonstrated that their telomeres were also short, that they died early, and that they lived in chronic ill health.² Spookily, two weeks before Dolly�s death, Matilda, an Australian cloned sheep, died unexpectedly at the youthful age of two years and ten months. Are clones, like the replicants in Blade Runner, doomed to early extinction? Typically cautious, scientists say they would have to study more clones to know for sure.

In death, Dolly continues her life of public service: Dr. Wilmut donated her carcass to the National Museum of Scotland, where it�s been stuffed and displayed.

Her surviving kin include 24 cloned calves; a cloned monkey, pig, cat, and rabbit; and a species of endangered Asian cow.

In Every Issue

Common Sense

By Invitation: Freeman Dyson

» Obituary: Dolly

From the Editor

1  Wilmut, I. et al. (2001) The Second Creation: Dolly and the Age of Biological Control. Harvard University Press.
2  Ogonuki, N. et al. (2002) Early death of micecloned from somatic cells. Nature Genetics 30:253�254.