The Genetics of a Great Racehorse

Sequencing the DNA of British racehorse Eclipse may help untangle the history of Thoroughbreds.

By Anne Casselman|Thursday, December 01, 2005

Eclipse is among the most popular racehorses in British history. Legend has it that his colorful owner, Colonel Dennis O'Kelly, placed a bet on the horse's maiden race, saying, "Eclipse first, the rest nowhere."

It wasn't long before entire grandstands were chanting those words. Eclipse easily won all 18 races he ran. More than 200 years after Eclipse's death, scientists are retrieving and decoding DNA from his remains, the first such recovery from a horse of an earlier era.

They hope to understand how Thoroughbred racehorses came about and how they developed. Little is known about the so-called founding sires before they reached England's shores.

But Eclipse can help sort things out. His great-great-grandfather, the Darley Arabian, is responsible for 95 percent of Y chromosomes in Thoroughbred males today. And Eclipse is in the pedigrees of 80 percent of modern Thoroughbreds.

DNA can tell researchers more than ancestry. In addition to reconstructing Eclipse's past, Matthew Binns, professor of genetics at the Royal Veterinary College in London, plans to create a genetic map of inherited diseases.

Meanwhile, Emmeline Hill, from the animal science department at University College Dublin, is examining parts of the Thoroughbred genome that have undergone positive selection. "This methodology might highlight areas that contain genes that are important for speed and stamina," she says. "So it might give breeders and owners an extra level of information."  

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