Jess at DesertWindHounds discusses the importance off genetic diversity in the Major Histocompatibility Complex (MHC), a gene family that controls immune responses. In dogs, it’s called the Dog Leukocyte Antigen (DLA) system
It’s very important that everyone in dogs understands these concepts.
In fact, it’s very important that everyone interested in conservation of endangered species or in breeding any kind of animal has a full grasp of the problems that can happen with reduced diversity in the MHC.
This angelfish website also partly discusses the MHC. Unlike Jess’s post, it is pro-inbreeding, but the author recognizes the need to bring new blood in.
The problem with dogs is we are operating within a closed registry or a Potemkin open registry system where new blood is not easily brought in.
And with virtually all Western breeds, all individuals within a breed are derived from the same founders.
The is the big problem with line-breeding, inbreeding, and using just a few sires per generation within a closed registry system. At some point, the breed becomes too homozygous within the MHC/DLA, and it’s screwed when a really bad disease pops up.
My guess is we’re going to hear a lot about the MHC in the near future. Many success stories of recovering endangered species are going to turn into disasters. Some species have recovered from a very low founding population, and that means that they don’t have much variation at all in their MHC.
That’s bad.
And there is one animal right now that recovered from intense persecution in its homeland. It was eventally protected, and its numbers grew.
But now because of a communicable disease, it may very well go extinct. As a species, it has low genetic diversity and very little variation in the MHC. If it does become extinct, it will be this compromised genetic diversity that ultimately does it in. If it had more diversity in its MHC, then some individuals might have a some immunity to it, but thus far, all have been found to be highly susceptible to this disease.
I’ll reveal that animal and its disease tomorrow in a longer post.
Until then, read this post and get a good understanding of what the issues are.
may we speculate on the species and the disease?
or would U it be a surprise?
Speculate if you want.
Some people already know.
I know! I know! Neenerneenerneener!
Arrgh, that’s spozed to be
“would U RATHER it be a surprise.”
The fish guy actually touches on a few things I’m going to talk about when I cover breeding practices. He is wrong, though, about one thing: there is no animal with “only desirable genes.”
Tasmanian devils and facial-cancer, a communicable neoplasm spread by bites.
there is a communicable cancer in dogs, too – an STD, i believe.
– terry
http://www.eurekalert.org/pub_releases/2006-08/cp-cci080706.php
This may sound uneducated but the angelfish guy sees that he is luckier that most other breeders, this is the key, right here and nothing more, but it still skews geneticists up big time:
“The reason inbreeding can be so effective with fish and probably not so effective with many other animals is because of the sheer numbers of fry that most fish produce. As fish breeders, we get to choose from many hundreds of offspring, which enables us to find the individuals (even if few in number), that contain the traits we desire and to “fix” them. It can require a lot of tank space and some very careful consideration combined with good judgment, but it is done all the time.”
It’s a numbers game and the number work in his favor.
That’s a pretty good point actually.
Yes, this is the same reason that inbred Corn isn’t as big of a problem (it can still be wiped out by a single disease though).
(1) Numbers of offspring to pick and choose from.
(2) Easier to cull 95% of fish than 95% of puppies.
(3) Time scale is shorter between generations so you can get what you want while you still have it in mind.
(4) We expect a LOT less of a fish. If they live 3 months, yay!
(5) No one is keeping a seed bank for dogs. GMOs don’t worry me as much when we CAN start over. There’s no reset button with dogs.
(6) Profit drives rationality. The only ones making a profit off of dog sickness or health are Veterinarians and Drug/Dog Food companies.
(7) Emotional attachment to any given fish or piece of corn is nowhere near (at least for me) my dogs.
Given a large enough population, you might even find that the longest lived individuals (not necessarily the healthiest) might even be slightly more inbred than the average person. Just like on the other end of the bell curve you would find that inbreeding also leads to more infant deaths and more infertility problems than average too.
We just don’t select for health with our inbreeding and we are so much more inbred than the beneficial (vis-a-vis longevity) individuals, we’re very likely to never find this magic bullet specimen that can be inbred on to fortune and glory.
The SLO study that DesertWindHounds references is recent:
“DLA Class II Alleles Are Associated with Risk for Canine Symmetrical Lupoid Onychodystropy (SLO)” Maria Wilbe, et al.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012332
Patrice
http://patricedodd.wordpress.com/
I didn’t get a chance to look that up, but thanks so much for the full link!
I pulled a bunch of studies from Pubmed when I was researching. I thought of your dog Cooper when I found that one.