Paw prints of selection
21 Jan 2010 by Evoluted New Media
With more than 400 distinct breeds, dogs come in a wide range of shapes, sizes and temperaments, and researchers have recently identified regions of the canine genome that appear to have been influenced by selective breeding.
With more than 400 distinct breeds, dogs come in a wide range of shapes, sizes and temperaments, and researchers have recently identified regions of the canine genome that appear to have been influenced by selective breeding.
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A border collie: one of the breeds used in the research. Others include Brittany, Dachshund, Jack Russell Terrier, Labrador Retriever and the Standard Poodle |
Dr Joshua Akey, assistant professor of genome sciences at the University of Washington (UW), and colleagues from the University of California, Davis studied 275 unrelated purebred dogs representing 10 breeds, examining genes for size, coat colour and texture, behaviour, physiology and skeleton structure for their possible role in variation amongst breeds. Akey believes the diversity among breeds originated in the last few centuries through artificial selection and strict breeding for specific traits.
Researchers catalogued more than 21,000 tiny variations in the genome and found that genetically, the German Shepherd, Shar-Pei, Beagle and Greyhound were especially distinct. The most differentiated regions included genes linked to hallmark traits of certain breeds – small size, short limbs and three for coats. Researchers calculated the overlap of signatures marking selection in the genome and found that 66% occurred in only one or two breeds, suggesting that it was likely that these regions contained genes that conferred certain qualities that distinguish breed. Signatures found in five or more breeds sorted the dogs into classes, for example, by size.
The 155 regions of the genome that appear to have been influenced by selective breeding contain 1,630 known or predicted protein-coding genes. The researchers were surprised to discover that genes involved in immunity and defence were overrepresented in these areas – natural and artificial selection was not expected to work on similar classes of genes – but noted that immune-related genes may be frequent targets of selection because of their critical role in defending against infection.
Researchers noted that although their work gave useful insight, the pattern of variation is unusual to the dog genome and doesn’t prove that a specific region is under selection. The research has the potential to advance knowledge about human genetics as it may be possible to locate gene targets of selection in dogs and map it to related regions in the human genome.
