Merle Pattern Buyer Beware

Merle Chihuahua, Buyer Beware

**FLASH** Germany bans the breeding of merle Chihuahuas
You can read about it on Merle Chihuahuas Pro Con Board. Topic Opposed...3 cheers for Germany

If you are thinking about purchasing a Chihuahua that is merle patterned here are few things you might like to know that you may not be told.
There is no proof that another breed was not bred to the chihuahua to get this pattern. So if you are purchasing this chihuahua as a purebred, you may want to look at a 5-6 generation pedigree. It has been proven that all merle chihuahuas go back to the same dogs. If you look at the genetics of chihuahuas, they do not carry the merle gene. Merle also very rarely, if ever appears from a mutation. Merle is also a very dominant gene. A merle only comes from a merle, there is no such thing as a carriers. So since chihuahuas do not carry this gene normally, it is my belief another breed was bred to one to get this pattern.
There are genetic conditions that come with the merle gene. If you do decide to purchase one, reguest to see the Parents along with your puppies CERF form along with their BAER form. CERF is a eye certification form that can only be done by a liscensed opthomologist. BAER is a hearing test that can only be done by a certified audiologist. These tests are commonly done on the current breeds that have the merle pattern. Shelties, Australian Shepards, Australian Cattle Dogs..etc. They have databases on these breeds. Chihuahuas, however, do not have such a database since the merle pattern has only been around for a few years.
Also remember that the puppy you purchase will have to be CERFed every year because something congenital can appear at any time.
The price of a dog should be based on the quality of the dog at the time it is sold and not on a color or pattern.

I have written to different geneticists for answers. I have received one reply so far.

My Email
I would like any information you may be able to provide me concerning the Merle Pattern Gene. I have been in Chihuahuas for 8 years and never saw a Merle. I have friend who has been in them for over 30 years and hasn't seen them either. They are now being produced. We have both been trying to prove that another breed had to introduced to produce this pattern. Are we correct in this? People are trying to say that it could be a mutation. I haven't found any information that backs that up. All I have found says that some colors can be mutations, but not patterns. Everything we have found says you must have a merle parent to get merle offspring. No dog carries the gene without being merle itself. Are we understanding that correctly? Any information you may be able to provide would be greatly appreciated. Thank you in advance

I was asked by my colleagues at TAMU to respond to your query on merle genetics.

At least nine genes are thought to be responsible for pigment and pigment patterns in dogs. The gene designated by the letter M has two alleles: the dominant M, which produces the merle pattern, and the recessive m, which results in the absence of the merle pattern. As far as we know, all dogs carry two copies of this gene. Those that are homozygous mm do not show the merle pattern (alternating light and dark areas, with the light sometimes being white). Those that are heterozygous (Mm) display the merle pattern. Those that are homozygous MM are usually solid (or nearly) white, often deaf, blind, and sterile, depending on breed.

According to the source I rely on the most, CC Little's book The Inheritance of Coat Color in Dogs (1957, Howell Book House, NY), the Chihuahua breed only carries the recessive m allele. However, this same source says that Pomeranians do not carry the dominant allele either, but I just saw a photograph of one, so this is not necessarily an absolute reference source. We don't know the location or sequence for the merle gene in dogs so I cannot say what sequence differences account for the two alleles. It seems highly unlikely, however, that a NEW spontaneous mutation in the recessive allele in your breed would produce the same phenotype of the dominant allele. I could not say this as an absolute, but in my opinion the merle has to have been introduced from another breed. Because the merle pattern is dominant, it could not have lain "silent" for many generations, only to reappear fairly recently.

This doesn't give you the black-and-white answer you would like, but perhaps it helps.

In a second email asking permission to post Dr Strain replied: "You are welcome to post my comments. I hope it would be clear that I am not attacking anyone. I am willing to try to respond to individuals who contact me."

George M. Strain
Professor of Neuroscience
Comparative Biomedical Sciences
Louisiana State University School of Veterinary Medicine
Baton Rouge, LA 70803
Voice 225-578-9758 Fax 225-578-9895
Research: www.lsu.edu/deafness/deaf.htm

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