I saved this material that someone sent me some time ago...it is very, very interesting.
> The genetic diversity idea began with people who were attempting to > preserve wild populations by breeding in zoos. They knew that a small gene > pool was a detriment to wild animals when reintroduced because they needed > the ability to respond to the pressures brought to bear by changing > environments. > This bandwagon was jumped on by dog breeders, but simply does not apply to > animals whose selection is done by humans and not by Mother Nature. > Genetic bottlenecks may be accidental or purposeful. An example of an > accidental bottleneck would be when the purpose of the breed > ceased to exist. Another accidental bottleneck occurred in a lot aof > breeds during WWII, when a lot of breeds in which the majority of the > population was still in Great Britain and meat was rationed. People were > forced to stop breeding and sometimes, dogs were destroyed because they > couldn't be fed. What was left is what breeders had to work with, and it > includes some health problems that can't > currently be tested for and which tend to occur after a dog has already > passed on his or her genes. Our cross to bear. However, even with a > VERY small gene pool, many individuals live a good long time in perfect > health and our task is to find a way to identify them earlier. > > Popular Sire Syndrome occurs when the bottleneck is purposeful (people > choose to breed to a popular dog) and certain deleterious genes are found > to > have been part of the package. Presumably these dogs are popular because > they > were excellent examples of their breeds, and therefore they must have > moved > the breed substantially in the right direction, even though there was a > price to pay. Guess what - there always will be. While we tend to think > that a > dog with no bad genes is the norm, quite the opposite is true. All dogs > possess genes for health problems - you just have to choose your devils. > The > only way to eliminate any of them is - you guessed it! -to narrow the gene > pool! > > Let me give you a scenario: There are three distinct lines of Liberian > Wufflehounds, developed by three old-time breeders. You know that one > line has a tendency to develop a fatal heart problem at age six. Many of > the > second line go blind at age five. The third line, which is yours, has had > an > alarming increase in a rare sort of liver shunt in recent years - hardly > a dog in your line exists who hasn't thrown it. You know it to be > recessive, and a blood test exists to tell which pups will develop it, but > there is > no test for carriers and no cure or surgery; it's uniformly fatal. What do > > you do? Do you: > A) Breed to an older dog from one of the other lines to avoid doubling > on the shunt? > B) Breed within your own line, test and cull the positives? > C) Get out of Wufflehounds? > > Let's look at the options: We all know that (C) is a cop-out. (A) risks > adding a problem you don't currently have to your own line. You might > get lucky and choose a non-carrier, but it's a crap shoot. This is the > Large > Gene Pool option, and if the breeders of all three lines think this way, > soon > all three problems will be well-dispersed throughout the breed. Triple > whammy. Trying to cover up recessives with desirable dominants is much > like > hiding your head in the sand. You will probably also lose your currently > excellent type and good movement, or at least make it far less > consistently > produced. (B) is your best option - you keep your type, and slowly reduce > the > incidence of liver shunt by removing the genes from the pool (i.e. > reducing the > size of the gene pool). Eventually you will have a litter with no shunt > puppies. > This will tell you that at least one parent is not a carrier. Further test > > breeding will tell you which one (Maybe both!!) Now - CONCENTRATE THESE > GENES! This is your job as a breeder! > > BTW, there is also a myth that you lose size, fertility and vigor by > inbreeding. Laboratory mice have been inbred brother to sister for > hundreds (maybe thousands) of generations in order to get a very uniform > population so that test results aren't skewed by differing genetics. The > mice of today > are larger, healthier and more fertile than the ones they began with. Why? > > Because they selected for those characteristics! That was the *standard* > that they wished the mice to *conform* to. You get what you select for - > what > you don't pay any attention to goes to hell in a handbasket. > > There is a website with an article by a truly knowledgeable breeder, or > stockman, if you will. It is long, but well worth the time. > http://www.alpacas.com/genetics.html > Don't be thrown by the fact that the site is about Alpacas - the > Brackett article is about dogs. Still, genetics are genetics. I will send more similar comments to the list in another post. Peggy ========================================================= "Magic Commands": to stop receiving mail for awhile, click here and send the email: mailto:[EMAIL PROTECTED]?body=SET%20CKCS-L%20NOMAIL to start it up gain click here: mailto:[EMAIL PROTECTED]?body=SET%20CKCS-L%20MAIL E-mail [EMAIL PROTECTED] for assistance. Search the Archives... http://apple.ease.lsoft.com/archives/ckcs-l.html All e-mail sent through CKCS-L is Copyright 2002 by its original author.
