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Merle chihuahuas?

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♥Cinnamon♥

I HATE BSL!!!!!
 
 
Barked: Wed Dec 13, '06 2:05pm PST 
I have a question if you breed a female and a male chihuahua together is there any chance you can get a merle chihuahua puppy in the litter?
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Gio

CD RE (CKC)- RXMCL (CARO) FM- CGN SJATD
 
 
Barked: Wed Dec 13, '06 2:18pm PST 
That depends if either of the dogs are merle. If you breed a merle dog to a non-merle dog you have a 50% chance of getting a merle pup and 50% of getting a solid colored pup.

The current belief is that if you breed two merles together you will get 25% solid colored, 50% merle, and 25% "double merle". In border collies, collies, and shelties this often results in a nearly completely white coat and vision and hearing problems. The genetic research currently being conducted is trying to figure out if these vision/hearing impairments are due to the actual merle gene or due to another gene closely linked to merle. As Great Danes, Catahoula Leopard Dogs and a few others don't experience the "double merle" health problems that Border Collies et al. seem to. So for the time being, until further research is conducted, it is advised not to breed two merle dogs together in order to avoid the risk of 25% of the litter being blind and/or deaf.
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Gio

CD RE (CKC)- RXMCL (CARO) FM- CGN SJATD
 
 
Barked: Wed Dec 13, '06 2:22pm PST 
In addition to my previous post, I must mention that merle is not a standard color associated with chihuahuas. Like in pomeranians and a few other breeds, there is debate as to whether the coloration was introduced through crosses with another breed or through naturally occuring (yet incredibly rare) mutations in the merle gene. Please note that if you are hoping to acquire a merle chihuahua, that you are probably not getting a purebred dog out of the deal. That somewhere back in the pedigree a chihuahua was crossed with another breed that has merle naturally in it. The merle gene is not one that can easily be hidden in pedigrees and definately not within a breed like the chihuahua. There is a condition known as "cryptic merle" where the only patch of merle coloration on the dog is either so small that it is overlooked or it is hidden beneath a white spot. Breeding a cryptic merle to another dog will result in normal merle pups 50% of the time.
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Kennitt

'It's all about- Me!'
 
 
Barked: Wed Dec 13, '06 2:26pm PST 
From Mom's little bit of research looks like Merle Chihuahuas are being bred for the pet market. It isn't a pattern that has shown up until recently and reputable breeders belive that there has been crossbreeding done to bring in the color.

It isn't an acceptable pattern for AKC shows and goes with the long list, mini, teacup, etc, all used to sell puppies.

Some great information is here:
http://www.tanyastoys.com/donotbuy.htm

Woof!!
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Zoey ( DOGSTER PHOTO CONTEST)

411177
 
 
Barked: Thu Dec 14, '06 12:46pm PST 
Actually ANY breed with merle can have "double merle" health problems - i.e eye and hearing issues. This occurs in MANY Catahoula Leopard Dogs as well as occasionally in Great Danes. Anytime that you breed merle to merle you risk getting double merles no matter what breed.
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Gio

CD RE (CKC)- RXMCL (CARO) FM- CGN SJATD
 
 
Barked: Thu Dec 14, '06 1:10pm PST 
There is research happening at this very moment into the association of vision/hearing problems with the merle gene. While the vision/hearing problems occur in double merled dogs, not all double merled dogs exhibit the problems. Hence the current speculation that the vision/hearing problems are due to the interaction of the merle gene with another gene to which it is closely associated. I guess knowing these tidbits prior to publication is a perk of my area of study. big grin

In no way am I attempting to refute the connection of double merling with vision/hearing problems, or imply that breeding of merle to merle is acceptable or advisable. I'm just attempting to point out that so very little is actually known about the genetic aspects of merle that it would be unwise to make vast generalizations. BUT that being said, as we do know that the majority of double merled dogs do have vision/hearing problems, it would be responsible of us, as breeders, to avoid the breeding of two merle dogs as to err on the side of caution, at least until more is known about the condition.
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Tohbi - Deceased- 10/04/2013

Blue-Eyed Devil
 
 
Barked: Thu Dec 14, '06 1:29pm PST 
Yes Zoey - I was going to mention that. There are many, many downfalls to the double merle. Great Danes and Catahoulas are often deaf, blind or both. They have allergies and genetic problems galore. There are many double-merle dogs that get lucky and suffer little effect, but they're very likely to pass on the recessive tendencies to puppies. In Catahoulas, the white pups were usually culled at birth (just passing on info, don't blame me - I don't breed dogs). Its sad to know that 10-25% of the pups would be killed from a litter of 2 merle parents.

Tohbi is likely double merle and is a bit directionally deaf. I would have neutered him anyway, but its good to know he won't pass on any problems to future dogs.
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Pugsley

I Might Be Small- But I Have It- All!
 
 
Barked: Thu Dec 14, '06 1:29pm PST 
what is a merle chihuahua? Or any breed for that matter...
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Tohbi - Deceased- 10/04/2013

Blue-Eyed Devil
 
 
Barked: Thu Dec 14, '06 1:34pm PST 
Hey Gio - I must have posted the same time as you - well said! I personally think that the merle gene relates to deaf and blindness in pigmentation near the optic and auditory nerves. White headed dogs are more often the ones who suffer. I have no idea why.

A merle dog is one with the flashy grey or red pattern. Tohbi is too white to be considered merle, but you can see the merle ticking pattern on his hind end and rear legs. They also tend to have blue or "glass" eyes due to lack of pigment in the iris.

edit to add for Cinnamon -
Two merle dogs will produce some solid puppies. These pups will have merle genes in them too, but look like solid colored dogs. If you breed two solid pups from merle backgrounds, you can get a few merle puppies. I thought I'd mention that just in case you get a mystery puppy in a litter. I didn't even know there were merle chihuahuas.

Edited by author Thu Dec 14, '06 1:44pm PST

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Gio

CD RE (CKC)- RXMCL (CARO) FM- CGN SJATD
 
 
Barked: Thu Dec 14, '06 2:09pm PST 
Actually Tohbi, I think you got merle a little bit confused. While yes, breeding two merle dogs will yeild some solid pups, it is impossible to get a merle pup from the breeding of two solid parents, unless one of those parents is a cryptic merle (that is to say, their merle coloration is hidden beneath a white spot or is so small as to undetectable unless you search really hard). Even if the solid pup is from two merle parents, there is NO way that it can pass on merle if it is bred again. Solid dogs have NO way of making a merle pup (unless of course it is bred to a merle dog, but then the merle dog is the cause for the merle pups).

There is only ONE gene that causes the merle phenotype, or appearance. When that gene is in the homozygous recessive form (that is to say, that both copies of the gene that the dog has are of the same form) and that form is lacking in mutation, then the dog will be solid colored. When the merle gene is present in the heterozygous form (that is to say, that one copy of the gene is recessive and the other copy is dominant, or has the mutation) then the dog will exhibit the merle phenotype. When the dog is "double merled" or has both copies of the gene in the dominant form, then you have a predominantly white dog with the possibility of vision and/or hearing problems discussed previously.

There seems to be a misconception floating around that merle is due to multiple genes. This is false. Only one gene and one mutation within that gene causes the merle coat color we are familiar with. Solid dogs do NOT have a copy of that particular forum of the gene, or to put it another way, a solid dog has two copies of the merle gene that are "normal". A merle dog has one copy of the gene that is "normal" and one copy of the gene that has a slight change in it.

The gene responsible for merle actually encodes for a protein that aids in the passing of pigment vacuoles up the hair shafts of the dog. When one copy of the gene is "messed up" then some of the proteins do not function properly so the full amount of pigment is not passed up the hair shaft. This results in some hairs being solid colored and some hairs appearing dilute (either black, red, or brown depending on the base color of the dog).

There was also mentioned (I think by Tohbi) that white headed dogs are more prone to deafness or eye problems. This is actually true, though is not always the case. The reason behind this trend is because, in fetal development, the precursor cells for nerve and for pigment cells are one in the same. As the fetus developes, the precursor cells migrate from the spinal column of the embryo in the direction of the head and then down the body. Once the precursor cells migrate to different areas of the body, they then differentiate to be either nerve cells or pigment cells. So that leads to say that a dog with fewer pigment cells on it's head (ie. white headed dogs) will have a greater likelyhood of having fewer nerve cells associated with the sensory organs of the head (eyes and ears). The migration of the precursor cells is regulated by many many factors, most of which are hereditary, but some of which are due to "dumb luck".

Another interesting side note is that the LAST area of the dog that the precursor cells migrate to is the "tip" of the chest. That is why, even in some purebred dogs, you will get a tiny white spot on the chest. Labs are very common for this, but they are not the only breed. Many people used to (and unfortunately, still do) believe that the white chest spot is due to crossbreeding. This is false!! It is just because the precursor pigment cells did not migrate all the way to the tip of the chest in that particular dog's fetal development. They are in no way any less "purebred" than the next dog! Just an interesting tidbit of info big grin

Edited by author Thu Dec 14, '06 2:21pm PST

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