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The Genetic Tide Continues to Swell: Will DNA marker research stop the flood?

by Jeffrey Bragg

From http://www.canine-genetics.com/tide.htm

The tide of concern about genetic health continues to swell within the purebred dog fancy, driven on by scrutiny from without. The threat of punitive legislation, already a reality in Europe, is widespread in the USA and the contagion seems certain to reach Canada as well. Conventional screening methods appear to be a proven failure as far as curing genetic disease (rather than simply reducing it somewhat). As veterinarian breeder Ms. Chidiac-Storimans once wrote in Dogs in Canada, “obviously, breeding clear to clear does not work.” Yet great optimism is expressed in canine journals despite the seeming crisis proportions of genetic disease.

DNA marker research now holds the limelight. The US$750,000 canine genome project at the University of Michigan, reported in the press in 1990 as expected to identify DNA marker sequences for over 400 canine genetic diseases, has actually established 625 markers and as a “demonstration project” was able to link one marker to a specific genetic disorder, copper toxicosis in Bedlington terriers. This and several other DNA tests for breed-specific disorders are now marketed by VetGen in Ann Arbor MI, where the University is also located. The Scottish Terrier Club of America recently paid US$50,000 to establish a DNA marker for canine von Willebrand’s disease in their breed; other breed clubs are reportedly queueing up to pay similar sums for similar purposes. Obviously there is money to be made in canine genetic diseases, though perhaps not by dog breeders.

Even if every breed club had that kind of money to spend on marker development, and every breeder could afford $50 to $135 per test for all his dogs, there would remain plenty of room for doubt concerning whether the strategy of DNA marker tests followed by radical selection and culling would solve the problem of genetic disease. Gene pools of purebred dog breeds, already stripped and impoverished of genetic diversity by twenty or thirty generations of inbreeding and selection, may not withstand a massive wave of radical selection followed by yet more inbreeding. What happens when all or most individuals in a breed tum out to be “carriers” of the same defect? Breed gene pools represent only a fraction of the total canine species genome. Genetic diversity in purebreds is limited from the outset, by selection inherent in breed development and by the sometimes distressingly small numbers of founder animals when breed registries are first established. A gene pool is like a bank account – you cannot make withdrawals forever and never make a deposit. Yet the closed studbook system prohibits making more than one deposit! The fetish of “breed purity” demands that after the founder registrations the stud book must remain forever closed to new genetic input. When examined closely this concept of strict breed purity must be regarded as a racist ideal, similar in nature to the “scientific racism” promulgated by Hitler’s Nazi party. Why do we denounce racism and eugenics on the human level, only to tum about and defend the selfsame ideals as the only decent norm for breeding dogs?

Any description or defense of a project involving breeding across existing breed lines for practical purposes, such as the Wirehaired Pointing Griffon Club of America project, is met with aggressive rebuke. If every effort to restore genetic health, hardiness, or working ability through outcross breeding is to be condemned as a betrayal of the “purity of the breed,” then the entire purebred dog concept may be doomed to failure through inbreeding depression, the general loss of vitality and viability. Those who are quick to stigmatise serious outcross programmes as “Foufons” and “crossbreds” betray their utter ignorance of population genetics, yet that ignorance still meets with general approbation. Too bad, because at this point, the application of population genetics principles may be the sole strategy that can possibly pull the purebred dog fancy out of its genetic dilemma.

Genetic diversity is held to be essential to maintain species soundness and environmental fitness, but genetic diversity is what most purebreds seriously lack. Responsible scientific opinion now connects this lack of diversity with the canine genetic crisis. However much the racist mind may condemn the idea, there is but one way to restore lost genetic diversity in a population, and that is by new gene inflow – in other words, by outcross breeding. When will the purebred dog fancy awake from its dream of purified bloodstreams and allow the new gene inflow necessary to restore genetic health to our dogs?

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Jeffrey Bragg is Chair of The Working Canine Association of Canada, breeds Seppala Siberian Sleddogs and resides in Whitehorse, Yukon Territory.

January 19, 1998

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