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Is brown (liver) classified as a dilution?

It seems to be listed separately in most of the articles I've read. However, It does dilute the intensity of black pigment which is by definition what a dilution does.

Dilution or not?

JNFerrigno Sun, 04/24/2011 - 01:46

I say yes it's a dilution. Liver is 'Brown' and 'Chocolate' right? It functions the same way in dogs as it does in rats?

Daylene Alford Sun, 04/24/2011 - 08:56
The gene apparently codes for one of the proteins that makes up the eumelanin pigment granule, so the bb granules are smaller and rounder in shape as well as appearing a lighter color than those of a dog carrying B.
This is from is this how it works in rats? I'm going to have to exspand the site to rats at some point aren't I? :rofl

Dogrose Sun, 04/24/2011 - 10:52

I woudn't call it a dilution, I would say a dilution is an effect where the pigment is sparser causing the colour to look lighter. In liver/chocolate there is no dilution effect of the pigment, there is full saturation, its just that the pigment granules themselves are a different colour. If it were a dilution of black the pigment granules would still be black but there would be fewer scattered through the hair. This is what happens with the blue- bb - colour. Chocolate/liver itself can be diluted or altered e.g combined with dd it becomes lilac/lavender. Also yellow dogs with chocolate look different, chocolate alters most other colours it is associated with it.

Yes we need a cat and small livestock (rabbits, rats etc.) colour site :D

Daylene Alford Sun, 04/24/2011 - 20:58

Been doing some research on this and are the D and B locus the same in rats as in dogs?

This is concerning rats

*D–Dilute Locus
This locus causes pigment to be globbed together in big clumps instead of being distributed in the normal, even manner. This lightens the appearance of the color despite the fact that there is actually more pigment in each hair. The pigment in these animals usually gathers at the base of the hair, and the tips tend to be light, which gives a ticked/silvered effect.

quote from
So if your definition of a dilution is that there is less pigment then (assuming rats and dogs are similar) then dd wouldn't be a dilution either.

And doesn't the same thing happen in some dilutions in horses? For example in dun there isn't less pigment in the hair it is just loaded to one side which affects how light reflects on the hair shaft.

rodeoratdogs Mon, 04/25/2011 - 09:41

When a dog is dd the color is overall diluted and not consentrated at the base of the hair.

As repeated throughout these lessons (J): Chocolate, despite its self-colored nose (which is what I think causes the confusion), is NOT a dilute. Chocolate can BE diluted (Pearl/Isabella), but it is not, in and of itself, a dilute.

The self-colored nose of the chocolate dog is caused by the double recessive of "bb" and these alleles' inability to formulate black pigment. This self-coloration has nothing to do with the "D-series," "dilution," or a Chocolate (Eumelanin) dog being "a dilute red" (Phaeomelanin).

So keep repeating... "Chocolate is NOT a dilute. Chocolate can BE diluted (Pearl/Isabella)."

Recessive d
"d" is the recessive gene (or allele) in this series. As a recessive (and as the only recessive in this series), it requires two "d" genes, or "dd," in order to produce a visibly diluted dog.

This dilution action primarily affects Eumelanin, or the Black or Chocolates areas of the coat, as well as the skin, eye color and nose leather. If the Phaeomelanin (tan or red) areas are affected, this effect is minimal.

The action of dilution is to reduce the expression of Eumelanin color, or to "dilute." Other genes are involved that impact the depth of color. For example, we discussed in the "B-series" how Chocolate coats can come in a variety of depths of color, from light chocolate to liver chocolate, depending on the rufus polygenes attached. In this same way, diluted dogs come in a variety of depths of color, depending on the rufus polygenes attached to other series' alleles, or to the amount of Eumelanin expressed - for example, the amount of Eumelanin expressed in a bi-color dog versus the amount of Eumelanin expressed in a sable dog (see the "A-series") where Eumelanin is restricted, but not in totality.

You can see this variation in depth of color in "Dark Blue" versus "Silver Blue" dogs. It's not that one is "more diluted" than another, but simply that the existing depth of color (determined by other alleles) is diluted.

Daylene Alford Mon, 04/25/2011 - 11:55

I have found several definitions of color dilution on the web and they all state that it is a dilution if it lightens the appearance. So to me that means that no matter what the mechanisms are if the appearance is lightened then it is a dilution.

I did email UC Davis about it. This is really bugging me and I want to make sure I have everything classified correctly. Hopefully someone where will be able to answer.

JNFerrigno Mon, 04/25/2011 - 20:14

This is from… is this how it works in rats?

I'm going to have to exspand the site to rats at some point aren't I?

Yes you are! I would love you for ever, and try to help as much as I could on that. The biggest problem you are going to come across, are 'custom made colors' that breeders come up with. I don't understand it all, mostly I think it's shade. However there are a few unique mixes of dilutions and you end up getting something that we call Moon Babies here in the south. I know the original breeder consulted one of the leading labs on rat research and at the time they didn't know what it involved, there was just some speculation based on bloodline. And there are always the random crazy mutation. Wish her photos were still up, but if you are really intrested in doing the rats, I can send you to a breeder/researcher who does all her own nicropsies and studies. She had a girl with a pattern mutation, who's offspring have immune problems not seen in other populations.

Any way, don't get me rambling LOL

As far as how brown works in rats compared to dogs. I think it's the same. (Different in mice due to the Agouti genes). I don't know the details on why it dilutes or anything like that. But I know that an aa/bb rat is brown, A-/bb is chocolate agouti (and it does dilute). A-/Bb and aa/Bb are recessive and allow for full pigment. A few years ago there was a debate on aa/Bb being a weaker black. I don't know if it had any relevance in the scientific community, but in breeders we were wondering if that was the case. Like I said, shade some times made one think we were looking at different genetic make ups. Just like in horses, we have a few different black coat colors.


As for the dilution debate, I have always heard breeders of horses, dogs, and rats refer to anything that lightens the animals base color (red or black) as being a dilution. Regardless of the location on the gene map. In this sense one isn't referring to dilution as Dilution (D-Locus) but as a description of the effect it has on it's phenotype to the naked eye. When I study equine color, or any animal for that matter, I find it easier to separate things as base, dilution, modifiers and patterns. And by the definition of dilution, it would be because it dilutes both skin and hair color. In a sense I guess it depends on who your reading audience is. But I would still want to see what UCD would have to say about that, because from what I can tell on her site, the author is just a breeder.

Daylene Alford Mon, 04/25/2011 - 20:40

I did get a response from UCDavis

There are two schools of thought and neither is wrong or right or they are both right however you choose to look at it.
Some view brown as a dilution of black, others view brown as brown and not a dilution. It's more a matter of symatics. It also depends on which breeder you talk to about their breed, some view brown as brown, others view brown as a dilution.

The person who replied had a customer service email address though :lol:

I wish I could find a genetics definition of dilution that would probably clear things up alot but all the dictionaries I try just have the chemical definition.

This is from the UC Davis website

Two copies of brown are needed to dilute black pigment to brown.

rodeoratdogs Mon, 04/25/2011 - 22:23

Hmmmmm, maybe I should call Animal genetics tomorrow, they are super good at actually letting you talk to someone phone. It would be interesting to see what they say about it.

Daylene Alford Tue, 04/26/2011 - 07:51

If you want to call them that would be great! I would love to hear what they have to say. Just make sure they understand I'm talking about a species wide definition of dilution just to be consistent. I did find this this morning. It's from the university of penn.

Talking about the D locus in dogs

In dd animals, the intensity of pigmentation (for both eumelanins and pheomelanins) is reduced in hair, nose, footpads, and iris. It appears this is due to a clumping of the pigment granules, rather than a decrease in melanin synthesis.…

So it does function the same in dogs as rats. There is no actual reduction of pigment just a modification in the way the pigment presents.

This is pretty strong evidence to me that if dd is considered a dilution bb should be also. After all, they are both just modifying the way the pigment appears not actually reducing the concentration of pigment.

rodeoratdogs Tue, 04/26/2011 - 08:50

Ok she said technically if you want to call it bb Dilute I guess you could, she did use the word Semantics LOL, but this is what she said that bb is a "modified" black pigment that only affects black and dd dogs are in fact "diluted" and it affects all colors not just black.

Daylene Alford Tue, 04/26/2011 - 09:49

In reply to by Daylene Alford

Oh thanks so much for calling!

What she said makes much more sense to me but we call silver in horses a dilution and it only affects black pigment. I wonder how silver actually affects the pigment?

I'll have to think about this for a bit I may decide to classify it as a modifier instead of a dilution.

Everyone that is involved in other species how is bb classified in those? I know there are bb cats and mice.

rabbitsfizz Tue, 04/26/2011 - 12:50

OK, I am a complete newbie on dog colour. I understood, and this is raking my memory and probably form before DNA (or the Ark) but did not Blue come from Brown X Brown , originally, and did not Isabella/Fawn (it is confusing to designate it pearl as it is not??? I am completely happy with Brown, Blue, Fawn (it's "albino" I am not happy with)) come from Blue X Brown??
This would indicate that there is some sort of diluting going on.
I found pretty much the same in Siamese points, Chocolate (brown) X Chocolate could give you Blue, then Blue X Blue or Choc could give Lilac- again, visual diluting going on.
Now, whether or not this is a true dilution, I am happy to bow to superior knowledge on, but it is certainly a visual dilution.

JNFerrigno Tue, 04/26/2011 - 17:55

Well this is what I know of rats and rat breeders. I actually emailed the few I'm still in contact with, and both used dilution and modifier interchangeably. However one breeder went on to conform the following:

In rats C is responsible for a true dilution, while D doesn't dilute at all, it just clumps the pigment together.

I still say it's a dilution, since effected animals have a noticeable lighter appearance.

But again, it just depends on your audience. I mean you can always add a note in there about how it works with pigment. But then you'd have to put the same clause in for D because it doesn't dilute either.

Looking at other breeder sites, it's accepted nomenclature in the community to use dilution for these genes, as well as many other genes. It seperates as base, dilution, and patterns.

This is a good web page for images, but I think they also some times use the word modifier when it comes to some colors.…

Jordie0587 Tue, 04/26/2011 - 21:58

I know that in dobermans anyway, Brown is recessive to Black and that the dilutions (blue and fawn) are dilutions of the two base colors and are recessive.

A blue is a dilute of black
A fawn is a dilute of red

A fawn is doubly recessive.

BB being dominant black and DD being dominant for non dilution (black or red)...

A black dog is either Bb or BB and Dd or DD
A red dog is either bb/Dd or bb/DD
A blue dog is either Bb/dd or BB/dd
A fawn dog is always bb/dd

I would (based on hairs themselves) NOT call a brown(red) doberman a dilute.

I've seen magnified images of doberman hairs and the black and red are identical except for the pockets of pheomelanin(brown/red) and eumelanin(black).

Dilute doberman hair is diluted because the pockets of melanin are larger, more irregular and more widely disbursed throughout the hair shaft. Instead of small, round, evenly spaced clumps, they are large, irregular and widely spaced. This is what gives the appearance of a lighter coat color. When viewed under the microscope though, they are still the same color melanins as in the darker dogs.

I have no idea how it works on nose and eye color though.

Daylene Alford Fri, 04/29/2011 - 13:26

I've given this alot of though and I think I'm going to go with the dilution route. I think its going to be easier for a newbie to understand. This is the defintion I'm going to use.

Dilution: a genetic mutation that decreases the visual intensity of pigment in the coat and/or skin.

I probably could avoid the whole argument though if I just put diltuions and modifiers on the same page

Jordie0587 Sat, 05/07/2011 - 00:51

In reply to by Daylene Alford

That just seems wrong since all that I've found (for my breed) is similar to horses in that red is pheomelanin and black is eumelanin.

Whichever you decide to use is up to you, I just think it would be closer to correct to go with red and black and modifiers like horses are lol. Horse genetics are relatively easy compared to dogs!

JNFerrigno Sun, 05/08/2011 - 01:08 know why it made sense to be suddenly.

I think it's because I've been looking at B as a dilution in Rats. But we should be looking at B in dogs the same way we look at E in horses?

B allows for black, b allows for red. Chocolate is Brown is Red, it's just depends on the breed. It also has different intensities of expression.

Where it gets confusing, is in dogs, isn't there an A and E locus. A causes the black and tan in dobies? (it does in Mice)

rodeoratdogs Sun, 05/08/2011 - 08:47

From the B series lesson on a Rat Terrier color genetics website.....

In the "B-series" we're only dealing with two genes. That makes it nice and easy. Even better, there's a simple dominant to recessive in play: "B" is dominant, requiring only one "B" gene to formulate black. "b" is recessive, requiring two "b" genes ("bb") to produce what we call "Chocolate."

Some breeds call Chocolate, "Red," or "Tan," but we've already learned that true tan and red is produced through Phaeomelanin, and when we're talking about the "B" series, we're only talking about Eumelanin.

Here is the rest of the lesson.…

I would like to know what all of your think of this lesson on Rat terrier color genetics, is it wrong really? It makes more sense to me even though it takes awhile to understand it all, dog color genetics is way more complicated that horse genetics IMO.

Dog like horses are red and black based. I think that it's as simple as choc is modified black and blue is diluted black.
Even though you could say they are both diluted by different "mechanisms", I would say choc is more like silver in horses, is silver a dilute or modified? It lightens the coat?
Choc/or brown if you want to call it that only effects black.

Daylene Alford Sun, 05/08/2011 - 16:09

Silver in horses is classified as a dilution.

I don't necessary think that she is wrong in saying that brown isn't a dilution. I just want to know why I should agree with her and she doesn't do a very good job of explaining why. Some of her statements I defiantly don't agree with.

[quote]The "b" gene is not a dilute, and dilution is not its action. There seems to be a great deal of confusion over whether Chocolate is a "dilute." Dilution comes from the "D-series" and has absolutely nothing to do with Chocolate. Chocolate can BE diluted (Pearl or Isabella), just as Black can be diluted (Blue), but Chocolate, itself, is not a dilute. For more on this subject, see the FAQ.[quote]

This is a misleading statement. Dilution does come from the D-locus but it is not the only dilution in dogs. Even if brown isn't a dilution there are others such as cream that definitely aren't at the D locus and ARE dilutions.

I've been talking with hoofpick and she says that all the dilutions in horses produce clear tips on the hair (even silver). I would really love for her to looks at some brown dog hair compared to black dog hair. Would you be willing to send her some hair samples rodeo?

There really should be a cross species definition of what makes a dilution.

rodeoratdogs Sun, 05/08/2011 - 17:18

Oh yeah I'd do that, I have both blue and brown, and I sold the pearl puppy but I keep in contact with that owner since this is the second puppy I sold her so if I wanted a sample of his hair I'm sure I could get her to send me some.

I was noticing on Tequila her the color of blue is consentrated on the tips of her hair at least on her neck area, not so much on her body.
Rodeo blue coat is very solid looking all over so far, but that doesn't mean it will look that way under a microscope. Makes me want to run out and buy one so I can look at their hair under it.
This first pic is Tequilas hair on her neck and the second is her blue patch by her withers.

Daylene Alford Fri, 05/13/2011 - 22:55

Well I finally got an explanation and a definition!

I finally thought to ask horsegen (duh :BH I should have done this at the start)

The conversation follows:

Technically, a dilution is anything that lowers the amount of pigment produced by the hair shaft. Less pigment = lighter hair color. This is not an absence of pigment, as with white spotting--pigment is still produced, but less of it.
This is the problem. From what I understand many of the "dilutions" don't actually reduce the amount of pigment. I was reading that dd in dogs loads the pigment to the tip of the shaft so that it appears lighter, it doesn't actually reduce the amount of pigment in the hair. From talking to hoofpick it seem that maybe dun and silver in horses do something similar as they load the pigment to one side of the hair shaft. Am I understanding wrong?



horsegen 05/13/2011 - 07:46 Delete Block
This theory is kind of fuzzy, because the idea of "loading" the pigment to one side of the shaft is hard to prove. (This is why I use words like "technically"!) In strict terms, less pigment is present on one side of the hair shaft in dun that because less pigment OVERALL is being made, or because less pigment is being made only on one side of the hair, or because the same amount of pigment is made, but it's all gravitating to one area? These are questions that are really hard to answer, because it's next to impossible to actually measure the total pigment molecules in a hair shaft! Microscopy is now suggesting that in some of these dilutions, one area of the shaft IS darker, so it seems that pigment is being "loaded" there...but does that mean that there's the same amount of pigment overall? Or is there still less than in a non-dilute animal?

Because these questions get very technical and are so hard to answer, we tend to still say that dilute animals show a reduction in pigment in the hair, therefore they are lighter. But certainly there are a number of ways of differentiating the various dilutions, and what this is teaching us is that as our knowledge of genetics and biological processes increases, it becomes increasingly hard to put a label on something!

You 05/13/2011 - 07:52 Delete
Got it! Thank you very much!

Last question: So brown (bb) in dogs would technically be a modifier since it doesn't reduce the amount of pigment (or move it in the hair shaft) even though the overall effect is one of a lighter colored dog?


horsegen 05/13/2011 - 08:44 Delete Block
Yes, brown is not considered a dilution. It is typically referred to as a modifier, just like bay or brown in horses. Brown is the result of a tyrosinase mutation, and as a general rule, any mutations in tyrosinase or agouti are called modifiers.

So there we go!

Lantokay Mon, 06/13/2011 - 13:24

My two pence worth: No, I wouldn't class it as a dilution. Think of the Dobermann.... In Black and Red (liver) Dobes, the rust markings are strong and deep red in colour, in fact there's not a lot of difference in the density of the rust markings on either.

Then compare to Blue and Isabella (Fawn) Dobermanns - both of which genuinely do have a Dilution gene (D) affecting the coat colour. The rust markings are also diluted to a paler tan.

So that example shows Brown doesn't actually dilute the colour as such.

Rats are *not* a great example to illustrate brown/chocolate/liver, lol.... since there really isn't a scientifically described Chocolate in rats - or at least, fanciers argue about it... I've only ever seen one or two rats in 30 years that I would really call chocolate and that was phenotypically.... You'd do better to use mice as a model for talking chocolate since they have at least 3 alleles on the B locus including two 'chocolate' browns - Chocolate, and the darker Cordovan.

With regards to rats there's a great deal of confusion also with Blue since there are two different, genetically unrelated Blues. One has the pigment clumping typical of D dilution, the other does not!

By the way, did you know that Blue rabbits don't show pigment clumping... Makes you wonder at the geneticists'definition of D Dilution, doesn't it? Unless in the rabbit, the hair structure has some part to play in that.