Understanding the Merle and Harlequin Genes
About the Merle Gene:
The merle gene is a pattern gene not a color gene!!! If you have a merle gene it is like throwing bleach on your dog, every where the bleach hits, the dogs color is diluted (this pattern is described as being displayed in torn patches randomly appearing on the dogs body) So, a black dog would be diluted to blue with black patches left and a blue dog would be diluted to a lighter blue or slivery color with darker blue patches and a tan dog would be diluted to a washed out beige with tan patches and so on...
About the Harlequin Gene:
The Harlequin gene is a separate gene that only works when the merle gene is present, so if the merle pattern gene is not present in a black dog but the harlequin gene is, then the dog will still be all black, and the harlequin gene does nothing, But when both genes are present then you get your white background and your colored torn spots...think of it like this, if the merle gene is like bleach then the harlequin gene is like bleach on steroids, or a bleach helper! And instead of just diluting the color of the dogs coat, it completely bleaches it out to pure white, so a black dog with both the merle and harlequin gene will have pure white with black torn patches, and a blue dog with both the merle and harlequin gene present will be all white with blue torn patches and so on...***All Harlequin dogs have the merle gene***
About the Double Merle Gene:
The double merle gene is the gene that gives us all the problems, because in this gene you can have hearing and sight problems...this is because the merle gene is a diluting gene which, when doubled, can affect the pigment inside the ear canal and inside the eye to the point that the hearing and or sight can be anything form slightly impaired to completely impaired, completely blind and or deaf, think of it like this, if the merle gene is like bleach and you get a little on your skin it is fine but if you use to much, handle it for too long (or get a double dose of the gene) then it can be very dangerous to your skin, and for dogs it is the same, a double dose of merle can be like adding bleach to their eyes and ears, you can get some damage, no damage or complete damage, now of course these are just examples to help the typical person better understand the complexities of genetics through relatable examples, and I know that it is not really like putting bleach in your dogs eyes and ears, that is unthinkable and painful, and to be blind or deaf or even have problems with it is simply a handicap and these dogs can still have perfectly normal healthy lives and have no other health problems, except for the eyes and ears, and the double merle gene does not cause degenerative hearing or eye sight loss, how well it see's or hears as a puppy is how well it will see or hear as an adult, now other genes can affect degenerative hearing or eye sight, but not the double merle gene, and that is a whole other article!....In a black dog, the double merle gene, when no harlequin gene is present, is expressed as a white dog with patches of black over blue (the white here is from the double merle and the patches would be your black dog with diluted blue patches) hince the name 'lethel white' as puppies born with only one merle trait would not have any white on them unless they had the harlequin gene...so when breeders saw a white marked puppy when there should be none, they cull it (killed it).... not all double merle have problems and many are still born completely normal, but the risk is still much higher in them... and lightly marked harlequins are still AKC approved to be shown and bred here in the States and a lightly marked Harlequin would be a double merle with the harlequin gene... this is allowed because the hearing and or sight loss is considered an injury resulting from the double merle gene not a genetic flaw...***Because even if a dog has eye or ear problems from the double merle gene this will not pass along to its puppies because it is an injury not a genetic defect*
How to NOT Breed for the Double Merle Gene:
How to NOT breed for the double merle pattern, as you would have to receive a set of merle genes from both parents to be a double merle, anytime you breed any merle pattern (harlequin is a merle pattern with a helping harlequin gene) to another merle pattern regardless of the original color of the dog (there are blue, fawn, brindle, black exct. with the merleing pattern) and you will get a portion of the puppies that are born double merle, but you can breed any merle pattern, even double merles to a non-merle pattern dog and have NO double merles in your resulting litter, a solid color dog, is any dog with-out spots on its body... white on the tows, chest and neck are fine as they come from a different gene entirely, as are mantles, fawns, blues, blacks and brindles. So if you want to breed a harlequin or a merle you should always breed it to a solid color dog for no double merle puppies
About the Double Harlequin Gene:
A note on double harlequin genes, there have never been any reported cases of a double harlequin, a double harlequin would produce all harlequin puppies as long as the merle pattern is present as well, as all harlequin litters are mixed with merles you can be sure that the harlequin parent was not a double, like wise a double merle will produce 100% merle pups no matter the other dogs genetics, a double black will only produce black puppies no matter the other dog is...now some genes modify existing genes so they can co-exits like merles and harlequins, or the fawning gene (a fawn is a black dog that has a gene that dilutes the black color to a brown color and then there is a masking gene which will allow the back to only be expressed at the points of the dog, nose ears, feet and tail :) and a double black dog with a merle gene will still produce the dilution pattern but the base color will still be black. As there are no double Harlequins, it is assumed that this is a lethal color pattern and the puppies will be die and be re-absorbed in-utero, shortly after the egg is fertilized, so to continue with our bleach analogy if a double merle is like leaving bleach on your skin for too long then a double harlequin would be like drinking the whole gallon of bleach and not going to the hospital...death, but without all the pain and agony, and this may explain why harlequins bred to other harlequins have smaller litter size, just a thought :)
More on the Merle Gene:
More on the merle gene, the merle gene is considered to be a very fragile gene, which means that is mutates easily, and that means that the pattern in which it dilutes the patches of the dog to, randomizes easily, hummmm, Some dogs have large patches some smaller, some have flecks in with larger patches (called ticking), some have flecks, small patches and large patches all together and these are all mutations of the merle gene, and can be bred for, in many other breeds esp. Australian Sheppards, the blue merle is a very desirable color and is bred for, even to the point of breeding for double merles! But also because this gene is easily mutated there are constantly new patterns and combinations of patterns being researched and understood, and even when breeding for a certain pattern in a merle, new ones will emerge, more so than in other genes, and that is what makes it a fragile gene :)
And there you have it:) some basics on the merle pattern gene and the modifying harlequin gene and you thought it would be hard:) ha ha :) if you have any questions please feel free to e-mail me
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