coloring question

[laurie etc]

Originally posted by missing lacy's impish son:

I find this very interesting as I once had a dog that was all white except a merle face. He was a rescue. He passed all physical exams and appeared to be quite healthy. At first we thought he was a double merle, but later figured he was a cross between a merle Aussie and a predominate white Border Collie. This made more sense as he appeared healthy.

Yep -He was probably what is referred to as a "color-headed white" and not a double merle. That happens in shelties, collies, aussies and BC's and usually, as you noted, they are healthy. Still a possibility that too much white around the ears can predispose deafness, but definitely not the same as homozygous merle.

[missing lacy's impish son]

One thing for sure, he had no trouble hearing! At times I had wished he didn't hear so well...

I have had two predominately white Border's. The other was white/black. He didn't hear me when he CHOSE not to hear me... The best description for his personality we could come up with was "opinionated".

[Mona Howard]

This is an interesting and basic lesson

on blue merle genetics:

 

This is and is intended to be a very basic explanation of the workings of the merle gene. If you already know about double merles and sable merles and such, you may not find anything new here, but you're welcome to stick around and comment. If you're not sure why people get upset about sable merles and double merles, stick around and learn.

 

There is no such thing as a sable merle gene or blue merle gene. There is only a merle gene. Merle is a dilution gene, that is, it lightens whatever the coat color would otherwise have been. The lightening is not spread evenly over the coat, but leaves patches of undiluted color scattered over the dog's body. Also, the lightening seems to work primarily on the black pigment in the coat, so any tan on the face stays even. Note that "black" as used here includes liver or chocolate. These colors are rare color faults in Shelties, but everything written here applies also to other breeds with the merle gene, including Australian Shepherds. A red merle in that breed is produced by the merle gene acting on a liver (solid red-brown, not the same as sable) coat.

 

One dose of the merle gene on an otherwise black dog produces a blue merle - a more or less bluish gray dog dappled with black spots. Tan points - the tan spots over the eyes, on the sides of the muzzle, on the legs and under the tail of a tricolor dog - will still be there in the merled tricolor. If the tan spots would not be present in a black dog, giving what is usually called a bi-black in Shelties, tan will not be present in the merled black either, and the dog will blue merle and white without tan: a bi-blue. One dose of the merle gene on an otherwise sable dog produces a sable merle. Sable merles are less predictable in color than blue merles, and may range anywhere from an apparent sable, often with a pinkish or orange cast to its coat, to something that looks like a very rusty blue merle. White markings remain on the merled dog, and may even be slightly more prominant.

 

Merle acts on the black pigment in the iris of the eye just as it does on the coat, so merle dogs often have part or all of the eye blue. (This does not affect their vision, though since it happens to some extent in the retina as well it may make it harder to diagnose certain eye problems.) The Sheltie breed standard allows blue or merle eyes in blue merles, but not in sables. Thus a sable merle with blue or merle eyes will not do well in the show ring.

 

Notice that I said a single dose of the merle gene. There are always two copies of a gene, alike or different, in any dog. If we call the merle gene M and the non-merle gene m, any given dog can be mm, Mm or MM. The mm dog is the normal, full-colored tri, bi-black, or sable in Shelties, or liver (red) in Australian Shepherds. The Mm Sheltie is a blue merle or sable merle, depending on what color it would have been without the merling gene. An MM dog, often called a double merle or a homozygous merle, will be mostly white and usually deaf or blind and often with other physical problems. Some MM puppies are born completely without eyes.

 

On average over a large number of litters, breeding merle to merle will produce one fourth full colored dogs, one half merles and one fourth defective whites. Breeding merle to full color will produce one half full color and one half merles, but no defective whites. The merle to full color breeding, then, produces just as many merles as does the merle to merle breeding, and without the danger of defective puppies. The safe breeding for a merle, then, is to a non-merle mate. This breeding should produce all healthy puppies, and about half will be merles.

 

To breed in this way, it is important to know which dogs are merles. This is one of the reasons experienced breeders rarely breed blue merles to sables, as this mating may produce sable merles.

 

Sable merles are no more likely to have health problems than any other color, and they are equally good companions. Many do have colors that are not accepted in the show ring, either because they have blue or merle eyes or because the mottling produced by the merle gene is too obvious. The real arguement against sable merles is that they may be mistaken for normal sables. If two such sable merles were mated together, the resulting litter could contain defective whites. What a shock for the breeder expecting normal, healthy puppies!

 

There is one kind of breeding that can produce all or almost all merles, and that is the breeding of a tricolor or a bi-black to a double merle - but remember that the double merle has a high probability of being blind or deaf. A very few breeders have been lucky enough to get high quality homozygous merles that are not too severely affected to breed - but it definitely takes a lot of luck and really top quality blue merles to start with. Merle to merle breedings are only for the very experienced breeder who knows her lines and what they will produce - and it has probably produced more heartbreaks than good homozygous merles, even for them. A blue merle from black to homozygous merle breeding is just as healthy as one from a more normal black to blue merle breeding. There are now three homozygous merles on the Register of Merit list: Merri Lon the Blue Tail Fly ROM, Shamont Ghost of a Chance ROM and Shadow Hill's Double Trouble ROM. Note that not one of these dogs is a Champion - double merles cannot be shown. Not only are Shelties more than 50% white severely penalized in the breed ring, most double merles have severely defective hearing, and a deaf dog cannot be shown at all.

 

Unless you have done a lot of merle breeding and really know what you are getting into, the safe rule is still that a blue merle should be bred only to a black (tri or bi).

[Mona Howard]

I forgot to state the above info came from

a sheltie genetics site. I am interested in

color genetics in animals. Mona

[Jennifer Glen]

This is an interesting topic. So, for those who know, is a red merle the same as a blue merle - with regards to being careful who you breed to? AND I have a weird litter to mention that I am not following the color pattern... My BC/rough collie cross is a sable tri (no tri points, the brown mixes with the black) his mother was a pure BC who was red and white and his dad was the BC/rough collie mix who was a sable (the male's mother was a sable too and may have been a pure BC) the litter produced sables, sable tri and a wierd merle that might have been a sable merle (sable head and legs but blue merle saddle). Does this mean the father must have actually been a sable merle and not just a sable? Judge for yourself if you remember the dog from Mad About You the TV show, Murray,that was the father to my dog. They were trying to get a double when Murray got old. He sure didn't look sable merle which is a color I do recognize since I have had 2 rough collies that color.

Jenny Glen

[Rebecca, Irena Farm]

I'm guessing the dog with the merle saddle was a very extended tri rather than sable. Think of it this way - the merle gene ONLY acts on the body color, period. So if you've got some solid color and REAL merle mixed you have to assume the merle part is the dog's actual "body color" - which is a totally unscientific and untechnical way of putting it but sometimes helps me sort it out.

 

Murray, huh? :cool:

[Eileen Stein]

>

 

Absolutely. Any dog showing merling has the Mm gene combination at the M locus, and can contribute either an M or an m to its offspring. And any dog who gets an M from both parents will be a double merle and be likely deaf and/or blind. Whether those merle parents are red or blue has to do with what's going on at another site on the chromosome (the B locus), and therefore has no effect on the double merle defects. So you don't want to breed two merles together, regardless of whether they are red merles or blue merles or sable merles or any combination thereof.

[Eileen Stein]

BTW, it's recently been announced that researchers at Texas A&M have discovered the exact gene and the specific mutation that causes merle coloring. It turns out to be the same mutation in all dog breeds studied, which implies that the mutation occurred way back in history, before breed differentiation. The same research team is continuing work to develop a genetic test which will show whether a dog is mm (not merle), Mm (merle), or MM (double merle). In the border collie one can usually tell this by looking, but the test would be useful in identifying hidden or cryptic merles (i.e., merles whose merling is limited to a tiny area on their body which can be overlooked), so as to avoid breeding such dogs to another merle.

[Pipedream Farm]

For those interested, here is a link to the scientific publication:

Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog

and the announcement and summary from The Great Dane Club of America which supported the research.

 

Mark

[lrayburn]

What's the difference between merling and the "roan" color exhibited by Australian cattle dogs?

 

Lisa

Nellie, Ben and Pip Squeak

[WWBC]

short, undetailed answer. Different genes. Ticking or roaning affects white areas. Merle affects/dilutes colored areas. Did you know Australian Cattle Dogs are white when born(except for any body spot they will have)

[Marty&Abigail]

what about mating two white/red border collie? could it be a problem? I know that some shepheds in england say that it is not a good thing..

[Rosanne]

white/red meaning predominantly red with white markings? So far I've never heard of a problem from this. Red is a normal recessive, so it has the usual RR, Rr, and rr alleles - a dog that has a red coat is rr, so bred to another rr will always produce all red puppies. I have heard some people say that this eventually dilutes the color or produces problems because it is recessive, but I have never seen any proof of this. More likely is that close linebreeding on a red dog could produce problems. Red is not a dilution gene, that is why it does not produce probems like merle does - merle affects the black/red allele by diluting whatever color the dog would have been.

 

Now if by white/red you mean predominantly white, that is always a bad idea (breeding two white dogs, I mean) too much risk of too much white on the heads/ears/eyes which is linked to deafness.