[You must be registered and logged in to see this link.]And inbreeding?
Inbreeding is where the sire and the dam are closely related: mother to son, father to daughter, sister to brother, half sister to half brother, cousin to cousin. People disgree about the exact point at which inbreeding becomes linebreeding. Inbreeding is the quickest way to find out what poor genes are in the line and what dominant characteristics are in the line.
Although many people are disgusted with the idea of this family incest, it is an extremely useful tool for diagnosing what genes are present. If the genes for bad eyes are present, but hidden or resessive, this will bring them out to their full extent. If there isn't any bad genes, then the puppies will be of very close uniformity and very able to reproduce themselves (theroretically). This is a homozygous breeding. The resulting puppies will have a lot of genetic material that is the same as their parents and grandparents and will be close genetically to each other.
Inbreeding doesn't introduce new genes and does not eliminate bad genes that the line already has. It only shifts them around like a rubix cube. This often results in litters with high show potential, if the quality was high to begin with. It shows you what recessives you have lurking in the dogs' backgrounds -- both good and bad. But there are drawbacks. Besides the possibility of bad recessives, inbreeding exclusively will eventually lead to infertility. It's like a xerox machine. After so many copies, you have to renew the ink. The same with dogs, you have to introduce new genes. No reputable breeder will use inbreeding exclusively, and many breeders simply never use it. Usually, you will only find: very experienced breeders, ignorant breeders, and puppy mills making use of this technique.
Inbreeding increases the chance that a gene obtained from the sire will match one obtained from the dam, both stemming from the common ancestor(s) on which the individual was inbred. Thus, inbreeding tends to make animals homozygous rather than heterozygous. The inbreeding coefficient measures the resulting increase in homozygousity. All breeds have a given degree of homozygosity the mating of two dogs from the same breed would not produce a recognizable specimen of the breed!
Inbreeding increases homozygosity and decrease heterozygosity. So it can duplicate both desirable and harmful alleles, both of which can be unsuspected in the line, and may appear. Inbreeding does NOT create anomalies, it brings present anomalies to the surface. Even when the anomalies are present, inbreeding might not reveal them. However, once revealed, then the breeder can do something about them in the next generations of breeding.
An increase in harmful recessives is undesirable but it is not a major drawback if they are identified early. The effect of inbreeding on major polygenic traits is greater. Generally, traits that are highly inherited (ie largely additively controlled) are not adversely affected by inbreeding but, traits under non-additive control, especially those tied to dominance and thus not of high heritability, are often markedly harmed by inbreeding.
[You must be registered and logged in to see this link.] 
Subject: Inbreeding websites 
Wed 25 Aug 2010, 9:02 pm
