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Maralynn

Tri Color Genetics

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Tess was born looking very black and white. When I picked her up at 7.5 weeks, still looked very black and white. Then at about 3 m/o I noticed very slight tan/brown patches on the backs of her legs. Those patches have expanded a bit in the last month and are now not hard to notice when she's got her butt toward you and her tail up. The underside of her tail is also a light color but I'm not yet sure if it's white of light tan (the color on her legs is light tan to rich brown)

 

So what exactly is this genetically?

 

Tri? Is muted tri a genetic thing? Something else?

 

Kolt has the same thing on the backs of his hind legs but not quite as pronounced as Tess. I believe that their dam is the same. I also know there are a couple dogs on her side of the family tree that are tri/brindle tri.

 

They both had a mix of (fairly pronounced) tri and B&W litter mates. One of Tess's looks almost like a kelpie in color. Kolt's sire is a tri, Tess's is B&W.

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Many tris show little tan when they're first born. People will look under the tail to see if there's a bit of another color there to get an early indication, so it's not surprising that this is where you're noticing it first.

 

My understanding is that tri is a simple recessive. So a tri parent will only be able to contribute tri to the mix, and two tris will produce only tri pups. But if mated with a bicolor the bi will predominate if that the gene the puppy inherits. Many, if not actually most, bis will carry the recessive tri. It just depends what that gene that parent contributes to the individual pup as to what's expressed.

 

The brindling in the points is the result of different genes. The dog is still a tri regardless of whether the points are tan, dilute (say in a blue or lilac dog) or brindle.

 

As always, if I'm mistaken, someone please correct me.

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I always thought that about Tri, too. But Kolt has several very B&W looking full siblings (he was from the second litter of the same cross). His sire is definitely tri. But if the dam was as well, why would so many offspring have traditional B&W markings? I have reached out to a few more owners of B & W litter mates to see if their dogs are all B & W or also have wisps of brown. Which, if they did, then I'll be satisfied that it's simply recessive.

 

(These are my deep ponderings for today as I walk behind my dogs and look at their butts)

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http://www.doggenetics.co.uk/black.htm#ghosttan

 

It sounds like this is what you're talking about it, or at least potentially. If so, it's a weird one.

 

2P11hpiJggvpNoKuF5Up.jpg

 

She was absolutely black and white when she came home - or very black and white looking.

 

3ptke0jW4TKgdFABF5Up.jpgNOPE.

 

People seem to want to say she's seal, but she's not. She's pointed. This isn't a great shot of her face, but you can sort of see that she has totally traditional tri tan placement there, too. (this is a good shot of the chest and legs). It's developed somewhat slowly over time, for a while it was only really visible in bright light, but it's become more obvious with age.


It's neat stuff.

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Yeah - like that! Though Kolt's patches haven't really extended past his hocks.

 

I have heard back from a few people who own his siblings. There are others with just a touch of brown or tan. But at least two are totally bi color as well.

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If I understand right, you can get the same variation in amount/placement as you would a tri dog. Which is to say that sometimes you don't get a lot and sometimes you do.

 

Neat, neat, neat thing that will never cease fascinating me. I'm glad you asked about littermates!

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I would show you a picture of mine but the stupid uploader won't let me. No matter how much I resize the photo, it still says it's too big, which is rubbish.

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Anyway, her brown started showing up on her back legs at around 7 months. I was told she was a ghost tri, though they didn't know the genetic implications of that, without testing her. Her dam did the same thing, and also has a little on her checks.

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Oh and reading back, the back/bottom of Molly's tail is not tan - she has tan around her tail but the underside is actually almost roaned. I *don't* have a picture of that, but it's weirder than the rest of her.

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Poking around a little on the web to see what I can find about tri- being simple recessive or something else.

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The at allele together with white markings produces the tricolour pattern. The transition of tan coloured hairs to dark hairs is very sudden. Tan markings occur in certain areas: above the eyes, on the cheeks, at the shoulder joint, the front and innerside of the elbow and the lower arm, the front and innerside of the knee and lower leg and below the tail. The dog must be homozygote atat) to have tanpoint markings. (http://www.bordercollies.nl/egenkl.shtml)

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Presence or carrier of tan marking

Presence or carrier of tan marking is caused by ASIP-gene (Locus A), particularly allel at. The allel at is responsible for the phenotypic colour black and tan (tricolor, tan). Locus A is influenced by lokus K. Phenotype can not be shown, if a dog has at least one of this allele KB (dominant black allele). Phenotypic colour black and tan can be shown, if a genotype is ky/ky ,ky/kbror kbr/kbr (https://www.genomia.cz/en/border_collie/)

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The tricolour markings show typically as tan spots above each eye, and around the face, the top of the front and lower coloured part of the back legs. With the tricolour gene, no tri or "tri switched off" is the dominant form so that dogs showing tricolour characteristics must carry two recessive tri (tri switched on) genes. Tri varies in its intensity and coverage, some dogs develop the full extent of their tricolour pattern only later in life, this can lead to confusion if a tricolour is not recognised as such before it is registered and its colour recorded. Tricolour pups are easy to recognise by a distinct patch of tan under their tail. (http://www.mastamariners.com/border_collie_colours_page-02.html)

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The table below shows the four main genes involved in determining coat colour in the Border Collie breed and defines the dominant and recessive form of each gene.

Genes Dominant Recessive

Gene 1 Solid Black Solid Red
Gene 2 No Tri (no tan) Tri (tan)
Gene 3 No Dilute Dilute
Gene 4 Merle No Merle ...

 

...Tricolour (black white and tan) Border Collies

The tricolour markings show typically as tan spots above each eye, and around the face, the top of the front legs and the lower coloured part of the back legs. Dogs showing tricolour characteristics must carry two recessive tri (tri switched on) genes. (http://www.readingdogwalker.com/2014/02/the-border-collie-dog-of-many-colours.html)

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These all seem to support my understanding that it's a simple recessive. I didn't find anything that contradicted this belief, though I didn't do an exhaustive search.

 

So dunno what to think about Kolt's apparently bicolor sibs. Unless there's a tiny bit of tan hiding somewhere unnoticed? I know I had one tricolor dog who had only had a very tiny bit of tan on her hocks and a few hairs on one cheek (mostly white face). Very light tan also. Few people noticed it at all unless I pointed it out to them.

 

And I think perhaps Molly's coloration has nothing to do with tricolor. A rare color variation? Perhaps influenced by the tiny bit of non-border collie DNA in her make up?

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And I think perhaps Molly's coloration has nothing to do with tricolor. A rare color variation? Perhaps influenced by the tiny bit of non-border collie DNA in her make up?

 

It is definitely a rare color variation, and it certainly could easily be playing off/from the bit ACD genetics (because the blues are all also tan pointed), but it is related to tri.

 

From the page I linked above:

 

On a dog with "ghost" tan, these points are barely visible. It's thought that this is caused by something similar to seal (see above), where the K allele for some reason allows the A locus allele/s to show through very faintly.

 

I don't now much. I don't think anyone knows much but I gather from a bit of digging that it can happen with any breed where tri-color or tan pointing is possible, and that the 'only faintly show through' isn't common/normal anywhere. It's just some genetic variation that, for some reason, only very faintly allows the tan to show.

 

If that's not what's going on with Kolt, I have even fewer answers about Kol's black and white siblings except degree varies and again, maybe they just haven't noticed. Riika using the term ghost tri makes me think her dog has the same thing going on as Molly, though.

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And now I'm digging more.

 

I found this on an english shepherd page:

Ghost Tri-color – Underneath it all, these dogs are genetically tri-colors/tanpoint. There is some variance in the black pigment so it is not completely covering the base coat color. This allows for markings to shine through especially on the face or legs. It may become more pronounced as the dog ages.

 

And this on an American Bully one:

 

A dog that is solid white, Dominant Black, or Recessive Red (e/e), but genetically at/at would simply be homozygous for tan points, not necessarily tricolored, because tan points would be hidden in those cases. However, such a dog would still be able to produce tricolored and tri carrier offspring. In cases of incomplete dominance, both Dominant Black and Tan Points may be expressed. Incomplete dominance is responsible for Ghost Tan and Seal.

(This might explain Kolt's siblings - the first half of it, I mean).

 


And this from a BC one:

Seal and Ghost tri both seem to occur when an unknown modifier acts on KB, allowing colour to ‘leak’ through, so a dog with a copy of ‘ay’ appears seal, one which is ‘atat’ appears ghost tri

 

That page actually has a lot of genetic info and some good in depth links: http://aviarybordercollies.com/Border-Collie-colours-and-why-we-test-

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It finally worked!

 

The lighting makes it hard to differentiate between the sun bleaching and the tan stripe...

 

She used to have some inside her ears as well, but those hairs disappeared.

 

post-15338-0-22354900-1504996097_thumb.jpg

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I don't mean to hijack the thread, but does any one have any knowledge of the "creeping tan" genetics?

 

I am pretty sure my boy George has it.

 

post-14654-0-02993100-1505085997_thumb.jpg

 

post-14654-0-49507900-1505086048_thumb.jpg

 

post-14654-0-01405800-1505086178_thumb.jpg

 

post-14654-0-39408200-1505086280_thumb.jpg

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