Hello,
Genetics is one of my favorite topcis to teach in my college bio classes and I often use canine examples. A large gene pool is theoretically great but is only useful if all members are participating in breeding. It is true that if all members of a *species* are interbreeding recessive diseases and health issues are much more rare. Please remember that in the case of a dog breed we are automatically dealing with an artifically-selected subset of the species so the gene pool is already reduced and modified.
In the case of show-quality dogs the gene pool is further reduced. Certain individuals and lines are used much more extensively and it's the care a breeder takes to *not* breed dogs with defects that matters. But we all know that there are breeders who breed dogs that have known defects because the value of other characteristics of the dog prevail. So we have to think about the actual gene pool that is being used - just because a breed becomes popular and more numerous doesn't solve any problems. This leads to the second issue, as we all know - back-yard breeders, often well-intentioned people who are just naive, that breed without checking for known disorders in the breed. They usually don't know what the issues are and certainly wouldn't pay the hundreds of dollars to have their dogs checked prior to breeding - even if they think they are going to make lots of
money selling pups. There is no quality-checking going on. In both cases (unethical breeder and back-yard breeder) the appearance of recessive genetic/health problems is not being addressed through good selection of the parents of the next generation. (Please realize I do know that sometimes these issues arise after a dog has been bred, sometimes extensively - but it's still the breeder's duty to make every effort to get that genetic set out of the breeding pool.)
Speaking to the choir here, I'm sure, but really, the only way to clear up these problems is for breeders to be responsible in their own crosses and for breeders to be sure pet-quality puppies they sell are spayed or neutered. Even the sale of show-quality puppies should include some assurance that the new owners have knowledge of possible genetic/health issues and must return to the original breeder before breeding their dog.
Personally I see trends in breeds that don't seem to make the breed more "popular" to the general public - such as the newer type German Shepard that crouches in the rear end and the changes in the Irish Setter prior to that. Somehow the breeds morph into new "trendy" forms and I'm not sure how that occurs - I certianly don't think it's a preference coming from the general public - except perhaps by the overdue influence of certain breeders?
Laurie
--- On Thu, 12/10/09, Amy Bailey <amy.bailey@myfairpoint.net> wrote:
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