Leefdaalhof - Page 2

thank you everyone.
Do anybody every breeds heavy on the linebreeding when it comes to Tom? 

Daryl...  I'm hard to insult, so we're all good. 

I apologize for simplifying the X factor breeding theory so much.  You're correct, there are other genes that come through, but they are not necessarily going to make a difference when it comes to working ability.  The X chromosome is the largest gene in the 39 chromosome pairs and carries 80% more material than the Y chromosome.  The X chromosome carries the genes relating to sex, reproduction, mental functions, muscle and some skeletal traits.  If you're going to look for a dog that has these similar traits to a dog in the pedigree, your best bet is to look to see what position that dog is in the pedigree and see if the X chromosome from that dog gets passed down to the litter you're looking at.  It's way more complex than even this, but unfortunately, I don't have time to get into it all on a message board.  

I've seen this theory work so many times, I have the tendency to put A LOT of emphasis on the X chromosome.  My bad!

One final thought...  You get far more consistent success when utilizing different breeding theories than when you're not, so why bother just winging it?

There's a link on Tom's page for "reverse linebreeding", which will show numerous examples of Tom linebred descendants, but unfortunately not in the order of "strength".  One example, the "Q-litter Vikar" is a 3-3 linebreeding on Tom, of which Querry Vikar would be a good example of k9gsd78's "black hole" pedigree.  Querry is certain to have Tom's Y-chromosome, but is just as certain to NOT carry Tom's X-chromosome.

The pic below show's possible paths of inheritance for a female's X-chromosome.  For a male specimen, you simply ignore the top half, as a male cannot directly inherit the X-chromosome from it's sire.  In Querry's pedigree, Tom occupies the #7 and #11 positions.  The Y-chromosome is 100% inherited from the top edge of the pedigree, from the sire's sire's sire and so on (#'s 1, 3, 7, 15...)  Querry could only possiblly attain his single X-chromosome from the ancestors of positions 12, 13, and 14 from the third generation, and not from position 11.  Therefore, it could be said that a 3-3 linebreeding on Tom (of #'s 7 & 11) would not have Tom's exact X-Y pair of sex chromosomes.



One of the nifty things about the sex-linked chromosomes, as that the probabilities of inheritance in further back generations is more heavily weighted toward specific producers than the normal laws of independant assortment would influence the genes located on non-sex-chromosomes.  In example, for a female specimen to have a "50% chance" of carrying an entire chromosome from position #20 in the fourth generation, I think is impressive.  Or, 100% for a Y-chromosome from #15 in the fourth generation.  So, when someone states that a fourth generation producer has no significance, that's not entirely correct.  In non-sex-chromosomes, inherited influence would basically be 50% from each producer of the first generation, 25% from the second generation, 12.5% in the third, and so on, halved in each preceding generation, the sum of each generation totaling 100%.

@ K9gsd78....I also tend to read pedigrees and make decisions based on the principles you have laid out.....don't know if it works....lol....but I usually have a pretty good dog at the end of the leash....smile.