The replacement of normal alleles with mutations will results in a decline in health and "vigor", including both genetic diseases and measurable traits such as reproductive success, lifespan, and survival. At this point, the population can be considered to be unhealthy, and the problem is the erosion in the quality of the gene pool.
We have had only very limited success dealing with problems like this. There is no easy way to select against multiple unknown genes, so usually animals are removed from the gene pool. But this rarely solves the problem. New animals similarly affected continue to appear, sometimes stimulating more research to find the offending mutations. Ultimately, the solution often becomes the removea of animals from the gene pool once again.
The problem isn't that the animal has a mutation; it's that it lacks a copy of the normal allele. Simply "getting rid" of the mutation will not solve the problem. The problem is not a malicious genetic bomb in the gene pool. It's the absence of the normal alleles that should be in its place.
What is critical for breeders to understand is that there is only ONE solution to this problem. It is to restore the alleles necessary to perform every function of the body of a dog. DNA testing will spot a few of the "bombs". But throwing those out still leaves a gene pool without the allelic diversity necessary to produce healthy animals. Every breeder knows from experience that trying to remove mutations by removing animals is fruitless; the result will not be a happy, healthy population of dogs.
Can you see that DNA testing to identify the few mutations we know about will not restore health to dog breeds? As long as the gene pool is closed, we cannot restore the gene pool to health and we will not be able to produce healthy dogs sustainably. If we want healthy dogs, we need to produce dogs with the complement of alleles necessary to support all the bits and pieces of function necessary to be a healthy dog. All breeds in a closed gene pool will already be suffering from a loss of alleles, some of which will result in loss of function. So, not only do we need to breed in a way that protects genetic diversity, we must take whatever steps are necessary to restore the diversity of the gene pools.
The solution to our problem is obvious and conceptually simple. It has been practiced by breeders of other animals for many years. There is no magic necessary, and it's not hard. You do need good information and guidance from individuals that understand the details of population genetics in order to accomplish the genetic rehabilitation of a breed effectively and efficiently. The sooner you start, the sooner we can be dog owners and breeders without also being experts in cancer, epilepsy, kidney failure, or sudden cardiac death.
Finally, the average dog lover is growing intolerant of the high incidence of health problems in purebred dogs. They identify the breeders as part of the problem, and they are not wrong. Pressure on breeders to improve health doesn't seem to be resulting in significant improvement, so the impetus now is legislation that will regulate dog breeding and make it illegal to produce animals that can be expected to suffer from health issues.
Breeders have experience in dog breeding. We must pair this with expertise in the proper genetic management of animal populations. To restore dog breeds to health, we must encourage and support this essential partnership.
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