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I have heard that white factoring for head means full white collar (just has to be all the way around the neck ruff to ruff, width doesn't matter), white extending to the corners of the mouth, and white blaze from muzzle (including corners of mouth) up between ears and connecting to ruff (which is all the way around the neck ). This is separate from white factored for body, which includes white up the legs and the white lightning bolt look on the hips. Further, there is a difference between "traditional Irish markings", which are white blaze, ruff, legs and tail tip, and "piebald", which is patches of black (or other color) and white all over, I think 50% of each.

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I have heard that white factoring for head means full white collar (just has to be all the way around the neck ruff to ruff, width doesn't matter), white extending to the corners of the mouth, and white blaze from muzzle (including corners of mouth) up between ears and connecting to ruff (which is all the way around the neck ). This is separate from white factored for body, which includes white up the legs and the white lightning bolt look on the hips. Further, there is a difference between "traditional Irish markings", which are white blaze, ruff, legs and tail tip, and "piebald", which is patches of black (or other color) and white all over, I think 50% of each.

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I believe my dog's father carried the gene for deafness however the owner said he seemed to hear fine. Another puppy from a different bitch they also discovered was unilaterally deaf. That puppy was traditionally marked and not obviously white factored however both parents (the merle father and black/white mother were). Obviously they stopped breeding that male. My dog's mother was almost completely black (white toes and a bit on her chest) and the dad had a bit more white up his back legs but less on his face.

I'm always really interested in conversations like this because genetics interest me.

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I wonder, though, if there may not be something more behind it than simply culling for an unwanted color.

 

I know of a family of border collies in which there's a high incidence of white dogs and overly marked whites. At least 2 of the white dogs from one litter are congenitally, unilaterally deaf, and one of them was born with an atrophied, non-functional kidney. He's also had more than average other health problems.

 

This is pure specualtion on my part, but it's made me wonder if there might be some correllation between congenital deafness and visual problems in white dogs and other organ system issues that may have caused a disproportionate number of white dogs to die as pups, or at least not to have thrived.

 

There IS actually some reason to think this, although I agree not due to anecdotal observations of outcomes in a single line with a lot of white.

 

First of all, there is a difference between white fur and unpigmented skin. Normal coloration for most mammals tends to be colored fur (white coats in winter aside), usually some sort of agouti color. Also, normal skin tends to have pigmentation (whatever color that is in the animal, be it black, brown, tan, whatever).

 

When you develop as a very young embryo, one of the first things that happens is that your cells differentiate into three main layers - an endoderm that a lot of your organs are formed from, a mesoderm that your muscles and bones form from, and an ectoderm. The ectoderm becomes skin and hair and oddly, neurons and your brain and sensory organs. Although it wouldn't seem so, we're all basically shaped like a big donut, meaning that although it is different tissue, the inside of your stomach and intestines, etc, are also formed from this ectoderm layer.

 

Since white spotting of hair and skin is typically not normal, it is usually caused by a mutation that affects the function of one of the genes in this ectoderm layer. Sometimes the mutation just affects coloration, but sometimes if the mutation is bad enough, or hits the right gene, it has other effects beyond whatever color effects you see.

 

In many mammals, it was known that white spotting was frequently caused by mutations in two genes, cKIT and EDNRB. Some of the mutations for these genes are mild and really only affect color. But other mutations for these genes can have much more wide ranging effects, causing defects in several tissues derived from the ectoderm, including intestinal and sensory issues:

 

 

Genes responsible for white spotting in mice and horses and for hypopigmentation defects in humans have been identified. One of these, EDNRB, encoding the endothelin B receptor, causes white spotting in the Ednrb mouse [3]. Some alleles of Ednrb are associated with more severe defects, such as deafness and aganglionic megacolon. Mutations in the endothelin B receptor gene are also responsible for Hirshsprung disease in humans [4]. This disease is characterized by intestinal aganglionosis, which is occasionally associated with hypopigmentation and/or deafness. A similar syndrome in horses, called lethal white foal syndrome, is due to a mutation in the horse endothelin B receptor gene [5,6,7].

Mutations in a second gene, cKIT, which encodes a receptor tyrosine kinase, cause the piebald trait in humans [8]. Piebaldism is characterized by white patches on skin and hair. In horses, a similar phenotype, called Tobiano, is caused by a mutation in either KIT or a closely linked gene [9]. A duplication of KIT causes white spotting in pigs [10].

 

HOWEVER, it turns out that white spotting and associated white skin in border collies is specifically NOT controlled by either of these genes:

 

"Conclusions

Both EDNRB and KIT were excluded as a cause of the white spotting pattern in at least two of the intercross progeny. Although these genes have been implicated in white spotting in other mammals, including horses, pigs, cows, mice and rats, they do not appear to be responsible for the white spotting pattern found in the Border Collie breed of dog."

 

From http://genomebiology.com/2000/1/2/research/0004/

I haven't read up on the latest studies that might show what does control white coloring in border collies, but I do think color genetics is a pretty fascinating subject!

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Thanks, Ooky. Interesting info.

 

I never intended the example I used to be "proof" of anything. It was just that, an example of a family of dogs that produced a lot of white and several with known deformities. (Btw, in rereading my own post as you quoted it, the dogs were bilaterally deaf, not unilaterally, as I mistyped.)

 

I'm well aware that it's far too small a sample to draw any conclusions from. It was meant to be another example, along with the white pups that my own dog had produced and someone's telling me about "white dog throwers" and (apparently a nonexistent) "lethal white factor" in BCs, that made me wonder about the possibility that there may have been some grain of reason, somewhere in the past that led to the bias against white dogs.

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I've had several white factored dogs over the years and am not particularly concerned about it as a health issue. Unless of course, both parents were merles. ;)

Rose is my white girl that I got from a shelter at 9 months of age. She has several health issues but the only one that could have any genetic components would be her eye issues. She had just started competing in agility and was taking agility classes again after a break when she began having issues. She'd always appeared to have some vision issues sporadically but this was bad enough for her to end up at the opthamologist. The opthamologist diagnosed her with early Immune Mediated Retinopathy or potentially early SARDs. I'm sure that if I took her to a different doctor she'd get a different diagnosis as opthamologists seem to disagree frequently. She's on immunosuppressants but I've noticed her issues returning sporadically lately. I do not know if Rose is a double merle or just white factored. She does have one "merle" patterned ear that may or may not actually be merle.

Loki is most likely white factored as well. He has a huge, full white collar, and white spots in the middle of his back. His dam was the same way and he has many cousins who are almost completely white. No health issues among any of them. I would not hesitate to get any pup related to him even if he/she were almost completely white. :)

 

My photos are too large of a file size to upload? Well, then here's a link.

 

Loki: http://www.flickr.com/photos/crawforddogs/8366692368/

Rose: http://www.flickr.com/photos/crawforddogs/8528548138/

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Don't hate on me here as we are passing anecdotes, but one saying in the horse world is that "grey is not a color, it's a disease."

 

Just more color myths passed down through generations.......sometimes you might wonder if it also is backed by wisdom of experience and not just purely anectodal?

 

Bonnie

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I have read somewhere, and I have no idea any more just where, that there are species where the rare or occasional white offspring is rejected by the mother, herd, or pack. Is it because the white animal has some sort of health issue which is not visible? The scholarly understanding was that the white animal, healthy in all aspects, did not have the camouflage protection afforded by the "normal" range of colorations. Therefore it was either more vulnerable to predation or less able to function as predator, or a combination of both - because it would be visible when it was beneficial to be less visible to potential prey or predator.

 

So, in some way, over many generations, did it become hard-wired into that species that a white individual was not a good thing and therefore would be eliminated by maternal or group rejection as an infant or young animal?

 

Food for thought. Or not! :)

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Don't hate on me here as we are passing anecdotes, but one saying in the horse world is that "grey is not a color, it's a disease."

 

My answer to that would be Desert Orchid. (Just google him.)

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My answer to that would be Desert Orchid. (Just google him.)

 

Or Milton, Abdullah, Gem Twist. There have been many famous and accomplished grey horses.

 

And then there is grey horse melanoma, which is what eventually would have killed my grey Thoroughbred mare Molly had we not put her down at the ripe old age of 29. Maybe in this sense, it is a disease - or at least a color prone to a disease.

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Reading some of these posts I wonder just how prevalent deafness that is not attributed to white factoring is in the breed and how many people are 'ignoring' the facts

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Hello everyone,


I am revisiting this thread to ask another question. Does at least one parent of a litter need to be white factored for the offspring to be white factored?


Thanks,

nancy

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Thanks, Denise! That's good to know.

 

Regards,

nancy

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