inbreeding, great article - Page 4

what about breeding lines to circles to get a polygon?

Thank you, Powerflex!

Much of this discussion is being based on Mendelian inheritance which is like trying to cover the field of mathematics with algebra only.

http://en.wikipedia.org/wiki/Mendelian_inheritance

The reality of modern genetics is that we don't understand much of what goes on and a lot of gene expression is based on environment sometimes in the grandparent's, parent's, or offspring's generation.  Therefore your breeding program for the GSD is confounded with the environmental conditions that happened in the grandparent's, parent's, and offspring's generation or lifetime.  This is why such things as feeding a food based on high carbohydrates rather than animal fats and proteins can change the expression of genes and why vaccines can have effects reaching into future generations.

Mendelian genetics does not work well with more than a single gene.  "A Mendelian trait is one that is controlled by a single locus in an inheritance pattern. In such cases, a mutation in a single gene can cause a disease that is inherited according to Mendel's laws. Examples include sickle-cell anemia, Tay-Sachs disease, cystic fibrosis and xeroderma pigmentosa. A disease controlled by a single gene contrasts with a multi-factorial disease, like arthritis, which is affected by several loci (and the environment) as well as those diseases inherited in a non-Mendelian fashion." (citation from Wikipedia)."  

Many, most and perhaps all genes are multifactorial when generational effects and environment are included in the model.  Mendel's laws were once all we had but they never were sufficient to cover all of the variability we see in genetic expression and none of the models we have now are sufficient either.  An arguement about linebreeding and open breeding is about as relevant as argueing whether steam or sail power is the best way to sail a ship around the world.