爱尔兰科学家５日发表报告称，基因分析证实，全世界现有５０多万匹纯种赛马都是生活在１８到１９世纪的２８匹马的后代。
１８世纪，英国人最早开始培育纯种马。他们用英国母马和驰骋在阿拉伯半岛的骏马交配，培育出特别适合长距离赛跑的马匹。如今，纯种马是世界上最名贵的马匹，由其而生的赛马业每年产值超过几十亿美元。
为了考察现代赛马的基因多样性，爱尔兰都柏林三一学院的科学家对２２１匹纯种马和１１７匹埃及马、土耳其马的ＤＮＡ（脱氧核糖核酸）微卫星进行了比较。ＤＮＡ微卫星是指ＤＮＡ基因组中小于１０个核苷酸的简单重复序列，又称短串联重复。
分析结果表明，全世界现有的５０多万匹纯种马都是生活在两、三百年前的２８匹马的后代。更让人惊讶的是，９５％的雄性赛马的Ｙ染色体来自１７００年出生的一匹阿拉伯骏马。
这种遗传学筛选方法同样适用于人类的进化和迁徙的研究，是经典的遗传学研究方法。
以下是英文原文：
Virtually all 500,000 of the world’s thoroughbred racehorses are descended from 28 ancestors, born in the 18th and 19th centuries, according to a new genetic study. And up to 95% of male thoroughbreds can be traced back to just one stallion.
Thoroughbred horses were developed in 18th century in the UK. English mares were bred with Arabian and other stallions to create horses with great stamina for distance racing. Today, thoroughbreds are the most valuable of breeds, representing a multi-billion dollar annual industry, worldwide.
To assess the genetic diversity of modern racing horses, geneticist Patrick Cunningham of Trinity College in Dublin, Ireland, compared 13 microsatellite DNA loci – repeating sequences of DNA which vary in length – in 211 thoroughbreds and 117 other Shetland, Egyptian and Turkish horses. He also examined studbooks dating back to 1791.
He found the majority of the half million progeny alive today are descended from just 28 “founder” horses.
It was already known that just a handful of stallions (but many mares) were used to found the thoroughbred breed. But startlingly, the new research finds that, in 95% of modern racehorses, the Y-chromosome can be traced back to a single stallion - the Darley Arabian, born in 1700.
Speedy selections
Related work on sequencing the horse genome is also uncovering genes in thoroughbreds linked to speed and stamina. Screening for these traits could one day guide owners' and breeders' decisions when buying horses, which may sell for many millions of dollars.
"We hope to produce sounder, faster and better-performing horses," says Cunningham. He and colleague Emmeline Hill at University College Dublin is also using the horse genome to uncover genes that explain why one animal runs faster than another.
"Horses are flight animals naturally selected for speed and stamina in the wild," explains Hill. "With domestic selection, speed was further augmented in the thoroughbred."
Thirty-five per cent of the difference in racing performance between horses can be explained by genetics alone, says Hill. She is cross-referencing up to 140 recently discovered human genes for fitness and performance in a bid to track down equine equivalents. These genes are involved in traits related to the cardio-respiratory system, muscle strength and metabolism, she says.
Bleeding lungs
However, the analysis of thoroughbred genetics is also revealing the other side of the coin, notes Matthew Binns of the Royal Veterinary College in London, UK. Many negative traits are associated with inbreeding in the diminutive gene pool, he says. "The selections we've made for fantastic beasts have had some detrimental consequences."
One tenth of thoroughbreds suffer orthopaedic problems and fractures, 10% have low fertility, 5% have abnormally small hearts and the majority suffer bleeding in the lungs, says Binns.
But as well as allowing breeders to select for performance-related genes, elucidating the horse genome may allow researchers to breed out negative traits, he says.
"Now we have a good amount of the horse genome, there are interesting times ahead," says Binns. "Over the next 10 years there will be some changes in this very traditional industry."
Cunningham presented his findings on Monday at the British Association Festival of Science in Dublin.
