The Dominant Black Gene - Page 2

The picture you posted looks more of a very dark black/tan, I wouldn't call her bi-color though she could be. The markings obove her eyes and on the chest plus the quantity of black on her legs and arms do not suggest she's a true bi-color. The dog in your avatar looks to me is a true bi-color and a very beautiful one.
 

Well... she is bicolor. :) She's a half-sister to the dog in my avatar, through the same dam. She's definitely a bicolor, complete with tarheels and toemarks and no tan behind the ears or on the back of her neck and no tan on her belly/chest.

Here's more photos of her:  https://picasaweb.google.com/100619446956993754435/BlackthornSHunter

You can kind of see the toemarks in this picture:



And the tarheels in this one:


This is her son out of Bandit v Wolfsheim (sable with black recessive)---he got the black recessive from his dad:




There are other examples, just harder to know details about dogs I don't own.

Here is a dog who I bet is also bicolor without the black recessive: http://www.pedigreedatabase.com/german_shepherd_dog/dog.html?id=627039

This female is a bicolor (blowing coat in the picture), who never produced black, even when bred to a black dog: http://www.pedigreedatabase.com/german_shepherd_dog/dog.html?id=462237

Christine
 

You have full extension of color or paling of color. But the different color genes in the GSD don't blend or mix like they do in horses or other breeds of dogs. For example, a black GSD bred to a washed out black and tan is not going to fix the paling. Unless the b/t carries the blk/r all they're going to produce is more of the same. " Inheritance of Coat Color in Dogs" by Clarence Little is a good resource.

BlackthornGSD,

You are the best one to know what color she really is and I take your word for it, but still she does not look like the typical bicolors I am used to, she even does not look like her half sister in the avatar, however her offspring especially the one in the last picture, the penciling leaves no doubt he's a true bi-color. Thank you for the additional pics and links.
I add: The two links you provided I doubt they're bi-color, though they never produced solid blacks or passed solid black genes they look to me dark b/t, they could have a recessive bi-color gene but they look more b/t to me and not true bi-colors, I could be wrong but no bi-color would have this much of markings on the cheeks. Wouldn't it be possible that your bitch also is b/t with bicolor recessive ?!!!!

Ibrahim 

I don't mean to drag this thread off topic, but my girl's mom Nike was a dark black-tan who produced bicolors and no blacks when her pups inherited the black gene from the sire. She also produced dark black and tans (saddle back).



She also produced bicolors--with and without the black recessive. I think Hunter (Nike x Alex) is bicolor/bicolor (bicolor from both parents) and Coal (Nike x Ashen) is bicolor/black (bicolor from mom and black from dad):



(Of course, if tan point (bicolor) and saddle are the same gene and it's all modifiers that make the difference, it gets a lot more complicated.)

Of the dogs I linked earlier, when Queen was bred to a solid black male, her puppies were bicolors. That makes sense if she were bicolor/bicolor. If she were black/tan-bicolor they look like Nike -- like a blanket back. I don't know that I could tell the difference between a dog that is blacktan/bicolor and one that is blacktan/black.

black-tan/bicolor (Nike)


blanket-back black-tan/black (Jubilee) (black gene from her dad, black-tan from her mom):


Coal (bicolor/black):


feel free to email me at giblaut @ gmail.com if you want,

Christine

Thanks Christine, I think I need to go through your last post several times to grasp and maybe look at the pedigrees but if I need to I will e mail you. Very interesting post this last one of yours.

Ibrahim

"I don't think it's one bit clear.  There's plenty of bicolors with recessive black and poor pigment, and plenty of showline dogs with no recessive black and great pigment.  Or should I say, "multitudes".  I don't think it's clear that recessive black has ANY influence on pigment. [except in it's homozygous state, in order to CONCEAL pigment]"


Daryl, there multiple threads on here discussing this.  Dark sables, commonly known as black sables in the GSD, tend to carry recessive black.  Now this doesn't mean that all dark sables will carry it, just that the presence of the rec black allele has an influence in pigment.  Also, not all dogs that carry it will be darker than average.  Likewise B&Ts. Not all are the same in intensity but information from experienced breeders on this forum does tell us that the presence of recessive black is likely to contribute.

The reason for the variation in pigment intensity is the influence of modifying genes.  All homozygous sables a^w a^w are not the same.  Likewise all heterzygotes a^w a^t, or all a^w a, or B&Ts  a^t a^t or a^t a.  We see a pattern of continuous variation influenced by the A locus alleles themselves, with modifier contribution.

Now this doesn't mean that all dark sables will carry it, just that the presence of the rec black allele has an influence in pigment.  Also, not all dogs that carry it will be darker than average. 

 

That disclaimer doesn't make anything "clearly evident" to me, just an opinion supported by subjective perception.

There's two types of pigment (melanin).
Eumelanin - dark brown and black pigment
Pheomelanin - red and yellow (blonde) pigment

Gain-of-function Agouti alleles and loss-of-function Mc1r alleles each cause a pheomelanic phenotype, loss-of-function Agouti alleles and gain-of-function Mc1r alleles each cause a eumelanic phenotype, and animals carrying combinations of Agouti and Mc1r alleles with potentially opposite effects exhibit a coat color phenotype predicted by Mc1r rather than the Agouti genotype; in other words, Mc1r is epistatic to Agouti.

~Mammalian Genome, Volume 15, 798–808 (2004)

Daryl, will you please explain how your above post supports your viewpoint.  Please - *in your own words*

Daryl, you have used text to illustate gene interaction between ASIP and MC1R to explain varying levels of pigment in the GSD in the past, but have so far failed to explain how this is relevant to the breed.  For this interaction to contribute to varying pigment levels, there has to be allelic variation at both loci.  Obviously this is present at ASIP, which is what is under discussion on this thread, but please say what you believe to be present at MC1R in the standard coloured GSD.

I want to know which form of pigment you are saying is "intensified" by the presence of the recessive black gene.  Eumelanin or pheomelanin?  Since one is epistatic to the other, I'm assuming you couldn't be referring to both.  So, I'm guessing eumelanin?  And if so, what is the appearance of "intensified" black?  Does it mean the black hair tips of sable dogs go further toward the root?  Are you saying that area coverage is increased?  I have no idea.  Like I said, it's not "clearly evident" at all to myself.