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Mule does impossible: Has a foal

NANCY LOFHOL, Seattle Post-Intelligencer
Published 10:00 pm, Wednesday, September 19, 2007
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The one-in-a-million foal born to a mule near Colbran in western Colorado in April is the mixed up result of a scrambled egg.

He's sort of a mule, but not exactly.

Named Winterhawk's Kule Mule Amos -- Amos for short -- the mule offspring most definitely is a scientific rarity called a "mosaic" that has researchers around the world eager to study the frisky, big-eared creature.

Mules aren't supposed to give birth. A hybrid of two species -- a female horse and a male donkey -- mules end up with an odd number of chromosomes. A horse has 64 chromosomes and a donkey has 62. A mule inherits 63. An even number of chromosomes is needed to divide into pairs and reproduce.

Genetic tests have found that Amos has some cells containing 63 chromosomes like his mule mother and other cells with 64 chromosomes like the donkey believed to be his father.

"When we look at Amos's cells it's very odd," said Lee Millon, the research associate who unraveled Amos' genes in the veterinary genetics lab at the University of California-Davis. "It's mind-boggling that this could occur."

"It disproves Mendel's law of independent assortment," said Dr. Roger Valentine Short, a reproductive biology researcher at the University of Melbourne. "This could make the front cover of Science."

Mendel's law dictates how parents transmit hereditary characteristics to offspring. But Amos broke that law and others pertaining to genetics when he was born. He shouldn't exist because his mule mother, Kate, should be infertile.

Amos turned up one morning peeking from under Kate in the corral at the Winterhawk Outfitters spread above Colbran owned by Laura and Larry Amos. The stunned Amoses had genetic tests done to prove Kate is indeed a mule and that Amos truly is her baby.

A second round of testing at the University of California this summer showed the egg that became Amos was an unexplained muddling of chromosomes. A similar case occurred in a foal in China in 2004. In that case, the mother was a hinny, a cross between a female donkey and male horse.

"When we see something like this it causes us to step back and take a second look," said Dr. Gordon Woods, director of the equine reproductive laboratory at Colorado State University. "This really challenges the way we thought things were."

Woods, who is famous in equine circles for cloning a mule in his former position at the University of Idaho, surmises there might be more cases of mules giving birth if there were more attempts to breed them.

About 50 cases of mules giving birth have been reported worldwide, but most of those were disproved or not scientifically documented. The mother turned out to be only a mule look-alike or the foal was stolen from another mother. Only a handful have been proved through genetic testing and most of those did not have scrambled genes.