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本帖最后由 细胞海洋 于 2012-8-30 12:37 编辑 , Q: a. B# ]/ q2 D' L
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4 D& T9 r8 |/ ~% C9 x4 V/ o7 vSome horses — notably the harness-racing American Standardbred and the all-terrain Icelandic breed — have the ability to perform extra gaits. All horses can walk, trot, canter and gallop, but some can also ‘pace’ — moving the two legs on the same side of the body in unison — and/or perform other novel ambling gaits. A genome-wide association analysis of Icelandic horses has identified linkage between a premature stop codon in the DMRT3 gene and the ability to perform alternative gaits. Functional studies in mice show that Dmrt3 is expressed in a subset of spinal cord neurons that are crucial for the normal development of a coordinated locomotor network that controls limb movements. Dmrt3 may therefore have a key role in configuring the spinal circuits that control stride in vertebrates. In domestic horses, the DMRT3 mutation has had a major impact on the creatures’ diversification, because the altered gait characteristics of a number of breeds apparently require this mutation. Cover: A competitor in the Landsmót International Horse Competition for pure-bred Icelandic horses, Hella, Iceland, in 2004 (Arctic Images/Corbis).
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