Deconstructing the Gene Pool
These adverse drug responses can cause illness or death in dogs that harbor the mutation, including nine herding breeds: Collie, Silken Windhound, Long Haired Whippet, Miniature Aussie, McNab, Shetland Sheepdog, English Shepherd, Aussie and Old English Sheepdog.
The ubiquitous working collies and spaniels of Europe spawned a number of the breeds created during the prosperous, class-conscious Victorian era. In the age of upward mobility, those on the way up claimed many of the privileges of the upper class, including the luxury of breeding, showing and “creating” pedigreed animals.
More than one-quarter of the world’s estimated 375 breeds were created between 1859, when the first dog show was held in the UK, and 1900, when Westminster and Crufts were well established; even the most subtle differences in weight or color were enough to allow registry of a new breed type. In many cases, the subdivision of farm dogs was an unintended consequence of competitive exhibition in dog shows.
Responding to the shows’ strict criteria for body type, size and color, breeders drew from an increasingly smaller number of founder populations to create dogs that conformed to these standards. Breeding closely related dogs to one another became a popular way to refine a breed, which today means a group of dogs with a common gene pool and characteristic appearance and function.
Unfortunately, the down-side of homozygosity (having two identical genes at a specific location on the DNA strand) can be disease and unsoundness. Partly as a consequence of this intense concentration on form, modern dogs suffer from more than 350 genetic illnesses, and today’s breeders bear the burden of restoring their lines to health.
A team of researchers led by Professor Mark Neff at UC Davis expanded the results of earlier research by demonstrating that the mutation probably originated in a single generic herding dog who lived in Great Britain in the mid-1800s. This dog must have been a common ancestor of founding dogs for nine different herding breeds, all of which were found to possess the mutation. Moreover, scientists involved in this study were able to describe the frequency of the mutation in these various breeds, further defining the inherited risk of adverse drug response.
Dr. Neff talked to me about his research and the implications of genetic testing on the health and well-being of dogs. Read the interview in the 2006 winter edition of The Bark, Deconstructing Gene Pools : Dr. Mark Neff and his team uncover the surprising origin of a potentially deadly mutation (The Bark, issue 34, Jan/Feb 2006). See photos of the afflicted breeds with frequency of mutations.
Jane Brackman, Ph.D
Dr. Barkman Speaks
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