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In 2006, two scientists, Clark and Murphy of Texas A&M University identified and sequenced the canine gene for merle. The merle gene was found to be caused by a mutation in the gene called “SILV“. The way the mutation occurs is called retro transposition. This is the ability for the piece of your dog’s DNA to actually jump out of the gene it is in during cellular division and genetic DNA replication. When the melanocytes (black pigmentation genes) are migrating from the neuronal crest during the embryonic development of the dog, the merle gene removes itself from the melanocyte genes (black pigmentation genes) and goes into the eumelanic gene (the gene that produces black, blue, grey, and dark brown areas in the coat).

In layman‘s terms, that means that the merle gene is an incomplete dominate dilution gene. This gene is a pattern modifier of whatever color genes the dog is carrying it creates a break in the color patter, causing the color to dilute in some areas, while leaving darker colored spots in others.

In ENGLISH, that means that the merle gene is an incomplete dominate dilution gene. This gene is a pattern modifier of whatever color genes the dog is carrying it creates a break in the color patter, causing the color to dilute in some areas, while leaving darker colored spots in others.

This merle gene is a dominate gene that is NOT carried recessively. If a dog is a merle, you will see it in one form or another. That can include merle markings that fade with maturation, one blue eye, or bits of blue in an eye, or any patch that is irregular in shape and not symmetrical can be an indication of the merle pattern. Anyone who sells a puppy that “carries the merle gene” claiming it’s a “hidden merle” and that the puppy can throw merle babies, when it’s clearly not a merle, should be looked into very carefully. Unfortunately, too many people know nothing of the merle pattern and make claims that they don’t understand and are untrue.

One parent has to be a merle in order to get a merle offspring. If the offspring has the merle gene than it WILL express itself (on average, half a litter will be merles). It is very important to carefully examine the pups as soon as they are born to identify ANY merle markings (as some markings will fade as the puppy grows), and to register these merle pups as merles on his or her papers.

There are such things as “hidden” or “cryptic” merles, but there are still ways to identify a dog as a merle. A “cryptic” or “hidden” merle is a dog that had visible merle markings at birth, but as the dog matured the merle markings disappeared. These dogs are still genetically merles and will produce merle offspring when bred. So it is very important to register these merle puppies as merle on his or her papers to help prevent the breeding of two merles unknowingly.

It is very important to never breed two merles together. Breeding merle to merle you may produce puppies that have hearing loss, vision problems, infertility, and other serious problems.

Some have suggested that merle appeared in the chihuahua breed from a cross to another breed, such as the dachshund. Others have suggested that the gene has been present for many generations but the dogs were incorrectly registered in their papers, such as blue and tan, or black and silver. At the bottom of the page, you will find links to websites that support the suggestion that it has been around for many generations and just been mislabeled.

After carefully considering the multiple petitions put forth by the anti-merle sector to disqualify the merle chihuahua for health reasons, and the evidence regarding the breeding of these dogs, along with the desire of the majority of it’s membership, the Chihuahua Club of America handed down its decision: To fully accept the merle chihuahua.

The AKC stand states that there is no disqualifying for color or patter within the breed. It states that any color, solid, marked, or splashed is permissible.

The AKC definition of merle: A marking patter, used in conjunction with another color. The color is characterized by a marbling effect of dark patches against a lighter background of the same color.

If you would like to know more about the merle gene, I have attached information about several other helpful websites. You just  have to copy and paste the web address.  Their information ranges from very specific and maybe a bit complex to “Genetics to Dummies” J . So browse through till you find one that makes sense to you. They also have different information in them, so reading one will teach you things that another did not cover. LOTS of info! Enjoy!

Dr. George M Strain, PhD, is a renowned scientist whose work has been the basis of the accusations for all of the health issues associated with the merle gene. This is a letter he sent Danna Ceja explaining the misunderstanding of his research. He submitted it to TNT after the misquotes that Gloria Lambert wrote in the June issue, he also sent it to Peggy Wilson President of the Chihuahua Club Of America to present it at the nationals.



This article is about doxies, but the same thing applies to chihuahuas.  So instead of breeding merle to merle, they say dapple to dapple.


This is a forum with lots of info, and people who can answer questions and offer support


Information about the accusation that merle is a color introduced from crossing to other breeds.  It also states that is they way we got our beautiful long coat chihuahuas.


Includes a picture of a merle dog from WWII published in “The First Chihuahua Book“-  Proof that the gene is not new and has been around for generations. (At the bottom of the page)