The genome of a domestic horse has been successfully sequenced by an international team of researchers.

一组国际研究人员成功解码驯马的基因族组。

The work, published in the journal Science, may shed light on（照亮，阐明） how horses were domesticated¹（驯服的，驯养的）.

It also reveals similarities between the horse and other placental mammals（有胎盘哺乳动物）, such as bovids（牛科动物） - the hoofed²（有蹄的） group including goats, bison（野牛） and cattle.

The authors also found horses share much of their DNA³ with humans, which could have implications for medicine.

Horses suffer from more than 90 hereditary⁴ diseases（遗传性疾病） that show similarities to those in humans.

"Horses and humans suffer from similar illnesses, so identifying the genetic⁵ culprits（犯人，罪犯） in horses promises to deepen our knowledge of disease in both organisms," said co-author Kerstin Lindblad-Toh, from the Broad Institute at the Massachusetts Institute of Technology (MIT) in Cambridge, US.

"The horse genome sequence is a key enabling resource toward this goal."

To generate a high-quality genome sequence, the researchers analysed DNA from an adult female thoroughbred（优良种） named Twilight⁶.

The horse's DNA was sequenced using capillary⁷（毛状的，毛细管的） DNA sequencing technology (known as Sanger sequencing) to reveal a genome that is roughly 2.7 billion "letters", or nucleotides（核苷酸）, in size.

In addition to sequencing the genome of a thoroughbred horse, the researchers also examined DNA from a variety of other horse breeds.

These included the American quarter horse, Andalusian, Arabian, Belgian draft horse, Hanoverian, Hakkaido, Icelandic horse, Norwegian fjord horse, and Standardbred breeds.

The team surveyed the extent of genetic variation both within and across breeds to create a catalogue of more than one million single-letter genetic differences in these breeds.

This is slightly larger than the genome of the domestic dog, and smaller than both the human and cow genomes.

So far, scientists have also sequenced the genomes of the platypus⁸（鸭嘴兽）, mouse, rat, chimpanzee（黑猩猩）, rhesus macaque（恒河猴） and, of course, human.

Horses were first domesticated 4,000 to 6,000 years ago. Over time, as machines have become the chief sources of agricultural and industrial muscle, those roles have shifted to sport and recreational activities（娱乐活动，文娱活动）.