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RMH

Coat color genetics

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RMH

 I think I have a fair understanding of genetics in general but I'm having some trouble getting my mind around the way the dilution gene works in dogs. This is the gene that makes Weimaraners gray instead of brown. The gene is recessive so it takes both parents being carriers. There are about thirty breeds that are known to carry this gene, and a few, such as Labs where it's shown up in recent years. Obviously it can be in mixed breeds and if the background isn't known could express itself unexpectedly. My question is can this gene have an incomplete diluting effect? I have found nothing stating this or anything research based suggesting it. I have a dog, 1 3/4 years old. He was given to me by my Son as an 8 month old pup. He is supposed to be a Brittany-Weimaraner mix. My Son saw the mother, orangish tan and white, short tail. Looked like a typical Brittany from the picture he showed me. The sire supposed to be a Weimaraner. No papers or suggestion that either was a registered dog. He got two as two month old pups just for pets. I know, two pups not a great idea. Anyway he was working full time at night and a full time college student days. His wife works full time days. At eight months they had two over active hellions on their hands. Hence, one came to me. The calmer of the two. He's turned into a nice dog, as has the other. They needed to be apart to get focused. My dog is a brownish/grayish color and white. A tad more white than colored. His ears are gray. Brownish/gray nose. His brother has yellowish/orange and white coloring, though he has grayish ears but a black nose. Both are naturally bob-tailed too.

 So none of the rules as I understand them seem to make sense as to the colors in these fellas. To top it off I asked my Son recently about the other pups in the litter when he got these pups. Some had long tails, some short. He said there was eight overall, with four orange or yellowish/orange and white. Two black and white. One brown[deep liver-chocolate] and white and my pup, a mix of dark brown, gray and white. He took the two bob-tailed ones. The added info of some having black in them confused me even more as to their possible ancestry. Both of these dogs will point birds, but neither has been encouraged to hold. My dog shows interest in retrieving. I'm not looking to make a real bird dog out of him but if it works out that he's useful he'll get some work in the woods. The coat coloring has me perplexed, especially the gray, which is brown diluted but in this case incompletely. Any explanations or reasonable theories appreciated.

 This is what an old guy with time on his hands contemplates during nasty winter weather. Research anything that looks at all interesting. I'll add that they both look like bird dogs. My dog is heavier built and the other has a smaller, more Brittany like head. But they both have a bird dog look. People always comment, I know that's a bird dog, but what kind?

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SLR

Well the bob tail mutation in the Brittany is a known one, and it is reported in the J. of Heredity 2009: 100(2) 236-240.  You can find the full paper online. I would give the url here, but I haven't figured out how to do the hyperlink thing yet. I researched this back when I was keeping the health database for the Small Munsterlander Club of North America. There were several cases of bob tail that happened in the SM, but they were clearly not the same mutation. The T box mutation is dominant. The gene codes for a transcription factor, so it could have effects beyond the tail length.

 

Many of the dilution mutations seem to be in the melanophilin gene. See: https://en.wikipedia.org/wiki/Melanophilin   J. Hered. 98 (5): 468–73. https://academic.oup.com/jhered/article/98/5/468/2187775  I can think of a number of scenarios for incomplete penetrance  for a single base pair mutation such as this one.  One possibility is that there occurs a back mutation during development, so that the dog is chimeric at that allele. It is now known through the extensive amounts of data from genomic sequencing of different cells from the same organism, that there are multiple lineages of cells, much like a genealogy tree for species, in the body as various mutations are acquired as cells divide and expand into various types of tissues. 

 

My understanding is that there are still quite a few genes that affect coat colors that have not been identified. Sheila Schmutz might be able to answer your question, if she is still active. See: http://homepage.usask.ca/~schmutz/dogcolors.html  Her contact info is at the end of the web page.

 

 

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RMH

Thanks for the information SLR. I read the info at the links. I'll try to contact Sheila Schmutz. Some of the reading was a bit over my head, I'll re-read it. Maybe it'll all be clearer the second time around. My post rambled around some. I could have been more to the point, which would be, can the dilution gene have an effect if only one parent has it and passes it to it's offspring? Seems like it shouldn't. So that would mean the mom was probably not a pure bred Brittany. None of this really matters. I find it interesting to try to understand the how and why of it all.

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DAP

What would really be interesting for the rest of us would be to see a picture of this dog.

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SLR
2 hours ago, RMH said:

 I could have been more to the point, which would be, can the dilution gene have an effect if only one parent has it and passes it to it's offspring? Seems like it shouldn't. So that would mean the mom was probably not a pure bred Brittany. None of this really matters. I find it interesting to try to understand the how and why of it all.

Quite right RMH that one would expect the Weim sire to be dd and the Britt dam to be DD, so progeny should be Dd for the dilution mutation. This genotype might decrease the amount of melanophilin protein production, but not enough to cause noticeable dilution of the coat color. Hence this dilution mutation acts recessively normally. It is not clear if what you see in those pups represents true dilution or some other complicating factor in the coat colors. I think it is unlikely the Britt is Dd, unless it is not a registered Britt with a record of being pure bred. Take a few photos to illustrate what you have there. On the other hand, writings about the coat colors in the Brittany breed standard state that washed out colors are not desirable. That suggests that they do occur, and no explanation for them has been stated. Maybe that is what you are seeing and interpreting as dilution.

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RMH

IF, very big if, I can figure out how to put a picture on I will. I have only recently joined the cell phone crowd. Yes, I was that hold out. I only have one because my daughter got it for me. I think it's so she can keep track of me when I'm out and about with "the little man", my three year old grandson. Getting wet and muddy is both our favorite things to do with the dog. Right now it's more wet and cold, but that leads to hot chocolate so it's almost as good as muddy.

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