Very interesting thread!
And along the same lines... I believe the gene that produces the "blue" in yorkies is the greying gene. Does anyone know how this works and whether it is dominate or recessive and how it expresses itself? I find this all so very interesting. Maybe it's because my husband and I both have browinsh hazel eyes yet both of our children have blue eyes.....

This is very interesting, I learned a lot! Now I know a bit more of what to say when people comment on how yorkies differ so much from one another. (in addition to poor breeding that is.)

Donna, that makes perfect sense when thinking of results. When I saw the word 'safer', I took it to mean safer concerning potential health problems. Assuming you were equally comfortable with the health background of either an outcross stud or one of your line, would you not have the added 'potential' risk of an unforseen health issue crop up with linebreeding that could become more likely the tighter the line?

I think rosemark was using 'safer' as you say and I was thinking about it in a whole 'nother way.

This is a subject I find fascinating yet some things just haven't gelled in my brain as I'd like them to. It's like I understand but don't quite *get* it as much as I'd like. I know some things only experience teaches but I love discussing things with those that have 'been there, done that'. It always leaves me with a better understanding of some facet of our Yorkies.

Also take into consideration when you bring in an outcross whether or not you are comfortable with the "potential" risk of a health issue you have to realize take Liver Shunt for example...you are taking a risk when bringing in an outcross not knowing if those two won't produce Liver Shunt even tho either line has produced it it can throw one because of a recessive gene you didn't know about even tho both parents have good BAT's. Some breedings just don't go well together. When outcrossing you are taking a risk. It is safer to line breed because mostly you know what's been thrown, type you like and if you've had no health issues it is considerably safer to line breed.
That is why we always say know your lines, know your health issues ect.
I don't mind an outcross when you've backed yourself into a corner as far as line breeding but you take the risk of bringing the undesirable traits when you outcross but can keep in mind you can bring in what you might be lacking in your own breeding. So it is actually safer to line breed than outcross :)

Donna Bird

Here is another interesting link on genetics. Some of you may have already seen this:
Relation

I've read that information before....there are quite a few software programs out there that will figure it for you. Here's an on line source you can try...

Inbreeding calculator

I'm still reading Genetics of the Dog plus reading on line....here's a fairly easy to understand explaination.

Do You Feel Lucky? - Genetics for Breeders, Part 1

Thanks for the links, y'all. I had seen most of the info before, but not from those exact links. I had never heard of kinship and relationship coefficients before, though.

I often see where the dangers of inbreeding are mentioned, but really, linebreeding and inbreeding so similar, differing mainly by degrees. Linebreeding is far more generally accepted but it seems that inbreeding is used very often in developing new breeds. Once developed, linebreeding seems to be the preferred tool used to maintain type while providing for genetic diversity. Would that be a fair statement?

I have read that Huddersfield Ben was the product of several successive generations of mother-son breedings so the very early Yorkies were highly inbred.

One notable group of dogs I've read about that are inbred is the seeing eye dogs. I have read that the average breeding coefficient is .25 among the ones bred in Morristown, NJ and that they are among the healthiest group of dogs anywhere. Theirs is a unique circumstance, however. Beyond rigorous health testing, those breeders keep their pups far longer than the average breeder and also have the advantage of closely following each pup throughout its lifetime so I'm sure they absolutely know their lines, regarding both health and temperament.

Donna, thanks for your explanation of line-breeding vs out-crossing. I'm at a point where I'm thinking about how to proceed with what I have. I have a very good quality bitch that I have bred to my stud and have had good, but inconsistent results. I think going back to my bitch's breeder for a stud might be the way I need to move forward. She has some wonderful dogs but isn't so much the 'mentor' type so I need to work on a better relationship with her so I may, hopefully, build for the future.

Here's a link to some interesting info I found...

Line Breeding

:thumbup: awesome thread!!! I love talkin genetics, but for some reason I cannot retain it and ALWAYS have to break out the biology books for reference :) and take great notes. This thread is a keeper in my favorites.

Thanks a bunch for posting on this topic.

I've heard that breeding Yorkies is part science, part art, and part luck. The science part alone is daunting for me, but some of it is starting to gel.

Below is something I copied and pasted from the link I posted. I find it interesting because I had never seen the importance of the dam emphasized so.


In all mammals the females are "X" "X" and males are "X" "Y" which means that only females carry the genetic code particular to the part of the gene string that is missing in all males. Horse Breeders refer to it the "X Factor" and have demonstrated that the gene responsible for the large heart so many great racing stallions have can be traced back thru their motherlines to a single mare that lived more than 100 years ago. If a stallion has an oversized heart - like Secretariat - this particular mare will show up in his motherlines over and over again. The mares themselves don't have the large heart but they carry the gene for it on their “X” chromosome. Like wise the stallions do not throw the large heart themselves.

And so it is with German Shorthairs. The bitches are far more important than the studs in carrying particular genes forward. Understand that this is true even if the genes most sought were originally found in a pre-potent male. The key for any successful Breeder is to isolate those females that carried his traits and breed off of them. It has been our experience that many important traits are indeed sex linked and carried by the dames from generation to generation.

Successful Breeders realize they are fighting "the drag of the breed," which is the tendency for all animals to breed back toward mediocrity. If it didn't work this way super species and super races would have developed long ago in every animal on earth. For instance in human beings it is impossible to breed parents with high IQs together to produce higher IQs. Even when two genius have children the average IQ of their children will be half way between normal and the average of their IQs.

It's not about Yorkies specifically, but it does make me think of things in a different way. I had read before of Huddersfield Ben being the product of several generations of mother/son breedings. The info I posted above helps put into perspective, for me, why it was mother/son rather than father/daughter breedings.