The horse genome: Riding high

November 5, 2009

The DNA of the domesticated horse shows evolution at work

THE genomes of many mammals have now been completed, including the cow, the dog, the chimpanzee and, of course, the human. This week it was the turn of the horse to have its DNA sequence decoded. With it emerged further evidence of how horses have been close human companions and, like other mammals that share an evolutionary history with man, how they could help the understanding of hereditary diseases. But there was also a surprise: horses have a newly forming part in their genetic make-up which shows the evolutionary process in action in a way that has not been seen before.

A team of researchers led by Claire Wade, then at the Broad Institute, in Cambridge, Massachusetts, collaborated on the project, which is reported in the latest issue of Science. They analysed DNA from a mare called Twilight (pictured above) to reveal a genome that consists of up to 2.7 billion base pairs (the “letters” in which the genetic message is written). This is slightly larger than the genome of a dog, but smaller than that of a human or a cow. They also compared Twilight, a thoroughbred, with members of other horse breeds. …

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