U.S. Team Produces First Mule Clone

Stefan Lovgren
for National Geographic News
May 29, 2003

First there was Dolly, the sheep. Now, scientists at the University of Idaho have successfully cloned a mule. Born on May 4, Idaho Gem is the first member of the horse family to be cloned.

The successful cloning of a mule, and the groundbreaking research on which it was based, could have a significant impact on fields as diverse as cancer research and racehorse breeding, according to Gordon Woods, a professor of animal and veterinary science at the University of Idaho in Moscow, who led the research team.

It's also the first clone of a hybrid animal. A mule results from a cross between a female horse, or mare, and a male donkey, or jack. As hybrids, mules are almost always sterile.

The birth, the culmination of a five-year process, was unassisted and went off without a hitch. Only 12 minutes after being born, Idaho Gem stood up, and 33 hours later he was let out to play on the grass.

"He was shooting around like a rabbit," said Woods. "I think he's very cute, inquisitive and vibrant. He's quite an athlete."

Soon, Idaho Gem will even have company. Two more pregnancies, resulting from the same cloning procedure, are in the advanced stages with the next birth expected on June 9.


Cloning has occurred in nature for billions of years in plants and some animals. The term refers to the process of asexually producing an offspring that is genetically identical to a parent plant or animal.

In the laboratory, scientists use cell nuclear transfer techniques to produce animals with genetic material identical to just one parent. Scientists remove the nucleus from an egg cell, which contains the cell's genetic material, and replace it with genetic material from another somatic, or body tissue, cell.

An electric pulse fuses the egg cell and the new genetic material. The cell is then treated in an activation medium that allows it to develop into an embryo to be implanted in a surrogate mother's womb.

While in-vitro fertilization in cattle is routine, it is rare in horses. Despite numerous attempts, only two "test-tube" horses have been born, back in the late 1980s. The low cell activity in equine species makes both in-vitro fertilization and cloning more difficult in horses than in cattle and even humans.

Idaho Gem's DNA came from a fetal cell culture first established at the university in 1998. For three years, the team worked without success. After transferring the nuclei from the mule cells into 134 horse eggs and implanting them into mares, only two pregnancies resulted. Both failed.

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