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[cmjust0]

How do you remove a recessive genetic trait once it's discovered without starting over with different animals? Even if you trace a particular recessive genetic problem back to one animal, without genetic testing, there wouldn't really be any way to look at an animal -- in most cases, anyway -- and determine whether or not the animal was free of the bad gene or was just a carrier for it...

Seems to me that all you could really do would be to either stop linebreeding to that animal so as to avoid passing *two* copies of the bad gene on to the next generation, or start breeding in different directions until you figure out which line hasn't manifested the problem in a long time..

I really don't know how it works, though...like I said, I prefer outcrossing even to purebreds, so I'm a little weird that way anyhow..

 

[freemotion]

Maybe she means cull the animal with the trait from the herd? That is the only way to remove a gene from a breeding program that I know of, once you know it is there.

 

[cmjust0]

Maybe she means cull the animal with the trait from the herd? That is the only way to remove a gene from a breeding program that I know of, once you know it is there.

Maybe..

Then again, I could stand another lesson in genetics, frankly.

 

[freemotion]

Yeah, I had it in high school biology, ninth grade, which was a frightening number of years ago. Of course, I have attended many lectures and read many articles and a few books on the subject since. Since the Human Genome Project was competed a few years back, a lot has been learned about genetics.

 

[trestlecreek]

Here's a link of interest:
http://www.ars.usda.gov/is/np/ha/han29.htm?pf=1

 

[kimmyh]

Line breeding is used all the time to refine and improve a species. For instance Min. Schnauzers have a recessive type of blindness, and in order to prove a dog or bitch does not carry the recessive trait, it is bred to a blind known carrier. If the puppies are all sighted, the dog or bitch does not carry the gene. This type of undesirable recessive removal would not be possible without dedicated breeders doing the unthinkable, and spaying and neutering beautiful known carriers. In goats it is the same, if an undesirable trait appears, you test breed to a goat known to carry the trait, and then evaluate the get. In line breeding i have never had an undesirable trait rear its ugly head, but if it did, I would place that particular animal and possibly its upline relatives in pet homes. Line breeding is not for the faint of heart, it takes a lot of planning, and someone willing to cut their losses and place beautiful show animals as pets.

 

[cmjust0]

Line breeding is used all the time to refine and improve a species. For instance Min. Schnauzers have a recessive type of blindness, and in order to prove a dog or bitch does not carry the recessive trait, it is bred to a blind known carrier. If the puppies are all sighted, the dog or bitch does not carry the gene. This type of undesirable recessive removal would not be possible without dedicated breeders doing the unthinkable, and spaying and neutering beautiful known carriers.

So..I have a question.

If you prove that a Shnauzer isn't a carrier for a blindness gene by breeding it to a known carrier, aren't you producing:

A) a litter of potential carriers, all of which will need to be spayed/neutered, or
B) a litter of blind puppies which will have to be put down

...all for the sake of proving or disproving the presence of a particular genetic problem?

And, another thing...isn't it fair to say that the genetic blindness problem altogether most likely the result of linebreeding at some level or another?

In goats it is the same, if an undesirable trait appears, you test breed to a goat known to carry the trait, and then evaluate the get. In line breeding i have never had an undesirable trait rear its ugly head, but if it did, I would place that particular animal and possibly its upline relatives in pet homes. Line breeding is not for the faint of heart, it takes a lot of planning, and someone willing to cut their losses and place beautiful show animals as pets.

I guess I see things differently.. What I mean is, it's not the faintness of my heart I'm worried about....I just wouldn't want to roll the dice on bringing animals into this world which I *know* have a pretty good shot at genetic abnormalities.

I'm not saying you're wrong for doing things the way you do them, or that it's patently immoral or anything like that...I just don't really agree with it, personally, for my own reasons.

But, hey...to each their own, right?!?

 

[trestlecreek]

Yep, this is one of those things that every breeder feels differently about!!!
Just from my opinion, I feel that disqualifying traits may be eliminated and physical confirmation may be uniform, but I don't like to play around with the other aspects.
There are many other genes that have to do with diseases and such and it can take years and years of breeding with no problems, then to have 1 animal pop up with a horrible internal problem,... when that comes out, then you have this problem linked back to many animals now carrying a bad gene.....
Scientists do a lot of work to see where and how this happens.
I actually love to read about this stuff, but the more I read, the more I find we do not know.......

 

[kimmyh]

The recessive blindness in Min. Schnauzers was there from the time of their importation, it would randomly pop up in litters across the country. When test breeding was initiated and slit lamp exams were the norm, more and more of the undesirable traits were removed.

The puppies from those litters were often put to sleep if they were blind, the ones allowed to live were spayed and neutered. It sounds cruel, but it is the only way to prove the recessive trait is there, or not. Once enough breeders cleared their lines, the Min Schnauzer world was much better off, and you rarely hear of people having Schnauzer puppies with recessive blindness.

The same thing happened in Collies, dogs that would go blind. It took many years, and a great deal of money to get a handle on the Collie blindness issue, but it has now become less of an issue in the breed.

In the case of the Min Schnauzers and the Collies, they were typically out crosses. So it took a lot longer to figure out where the problems were coming from and eliminate the source.

 

[cmjust0]

There are many other genes that have to do with diseases and such and it can take years and years of breeding with no problems, then to have 1 animal pop up with a horrible internal problem,... when that comes out, then you have this problem linked back to many animals now carrying a bad gene.....

I remember reading about something like that in horses at some point.. Don't remember the breed, but there was apparently this one big fancy show horse that everybody wanted a piece of, so it wound up in all kinds of lineage -- on both sides of the ol' family tree -- for that breed.

Well, as it turned out, that particular horse had some weirdo genetic condition that tainted thousands and thousands of animals..

Someone here knows what I'm talking about, I'm sure.. Can't remember the breed, nor the horse's name, nor the condition right off hand..