Twilight, a mare whose genes have been used to help map the horse genome.
An international team of more than fifty scientists, including researchers from the University of California Davis, have recently published the complete horse (Equus caballus) genome. The researchers present their findings in the latest issue of the scientific journal Science. Genomes are complete genetic maps which serve as the blueprint allowing living organisms to grow and reproduce. Genome research, often termed genomics, can provide valuable insight into diseases, evolution,and, in the case of domestic animals, the history of domestication.
A comparison with other recently completed genomes revealed that horses have larger genomes than dogs, but somewhat smaller genomes than cows or humans. Different horse breeds were also found to be more genetically similar than many dog breeds. The Takhi (Equus caballus przewalskii), a highly endagered wild horse from central Asia previously considered a distinct species, was found to be genetically indistinguishable from the domestic horse - possibly a product of extensive crossbreeding between wild Takhi and domestic horses.
The new study corroborates previous hypotheses regarding the original domestication of the horse approximately four thousand years ago. The genetic diversity found in the sex-linked X and Y chromosomes among different breeds suggests that the original domestication event involved numerous females but only a relatively limited number of males.
The researchers also found the genes behind the spotted coat of the Appaloosa breed, and discovered a suprising reorganization of the chromosomes that may provide a clearer picture of how large-scale changes in genomes take place. The new study demonstrates considerable genetic similarity between horses and humans. This similarity may have important implications for understanding and treating hereditary disease found in both humans and horses including infertility and muscle disorders
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