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4. Frequently Asked Questions (FAQ) and Genetics of the Turkish Van
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An example of an all-white Turkish Van As mentioned before, a minority of breeders is against recognition of the all-white Turkish Van for different reasons, often based on inaccurate or wrong information. For example:
- The white Turkish Van is a product of mating Turkish Van and Turkish Angora. - All-white cats are deaf and by using white Turkish Vans for breeding, also patterned kittens will have hearing problems. - Breeding patterned to all-white Turkish Vans will start producing offspring that are progressively less marked or more marked. - Breeders that do not want to work with all-white cats, will suddenly have unwanted all-white kittens in their litters, because all-white Turkish Vans can be find in the pedigree. As said, these reasons are often based on inaccurate genetic information. Therefore Dr. Leslie Lyons of the Feline Genome Project at UC Davis was contacted to give her expert opinion addressing the problems that would arise from patterned to white breeding. 4.1 Question: Dominant white, Epistatic white and the white masking gene are all the same thing. The cats that are in the Turkish Van breeding programs are homozygous piebald (SS) and homozygous piebald with dominate white (SSW). Answer Dr. Lyons: I have not heard these terms used before our discussion. Dominant white is epistatic to all other colors, meaning it overrides the other colors, hence, "masks" the other colors. So, I think these are all the same idea. Dominant white causes a cat to have few, if any, melanocytes, the cells that make pigment. If these cells are not present, then, no color can be produced, although the cats have all the other genes required to make color. Dominant white has two alleles (W, w). W causes no melanocytes. If a cat is WW, I am not sure what happens, they may not be viable, never have seen data on this. It could be obtained from any breed with dominant white. 4.2 Question: Dominant white will function in Turkish Vans as it functions in any other breed of cat. Dominant white is a dominant gene. Tithe gene is present in a cat, it will be expressed - the cat will be white. The only health risk associated with dominant white is the possibility of deafness. Answer Dr. Lyons: Correct. 4.3 Question: The patterned offspring from a patterned to white breeding have no greater incidence of deafness than the general cat population. Answer Dr. Lyons: Correct. If the dominant white cat is Ww, then 50% of the offspring should have pattern. The risk of deafness would be the same as any other Van patterned cat. I have not heard of confirmation that Van patterned cats, even with blue eyes, have deafness. I did ask European group about this as I thought they were collecting information, but, not sure if that ever happened. 4.4 Question: If the cat is not white, it does not carry the masking gene. It cannot pass the marking gene or possibility of deafness to it's offspring. Answer Dr. Lyons: Correct. 4.5 Question: A Van patterned cat bred to a white Turkish Van will produce offspring that are either Van patterned or white (masking the Van pattern). Answer Dr. Lyons: Correct. BUT, we are assuming that dominant white and white spotting is acting as two different genes. This is not known for certain. However, I would bet that a homozygous dominant white (W, W) is not viable and perhaps dies in utero and we never produce these kittens. 4.6 Question: Breeding patterned to white will not start producing offspring that are progressively less marked or more marked (to the point of solid colors other than white). Answer Dr. Lyons: I would think this has nothing to do with breeding to dominant white but the variation in the alleles one can have that produces bi-color. I do not think there is only one bi-color allele, S, in the world, and hence, when these alleles get mixed and matched, you get weird patterns. I think, for example, that Ragdolls may have various alleles at the white spotting gene. 4.7 Question: The piebald gene is not predictable. The spotting associated with the spotting gene is random to a certain extent. Under marked and over marked cats, as well as 'perfectly" marked cats, can all occur within the same litter. The dominant white gene will have no effect on the amount of spotting in a patterned cat, except to mask the pattern. Under the white, the cat will still be Van patterned. Answer Dr. Lyons: Correct, part of this variation is the randomness of cell migrations and the background genetics of the cat that interacts with the cell migration. Also, see above, there may be more than one bi-color allele and when mixed, may give unpredictable patterns. 4.8 Question: While a "grade 10" piebald (solid white from 2 piebald parents) is genetically possible, that white cat would not produce solid white kittens with any degree of predictability. Answer Dr. Lyons: Correct. 4.9 Question: A white cat that is dominant white will predictability produce an average of 50% white cats and 50% patterned cats when mated to a patterned cat. Answer Dr. Lyons: Correct, provided again, it is not WW, but rather unlikely these exist. 4.10 Conclusion Van-patterned kittens out of an all-white and a Van-patterned parent, will not have a higher risk for deafness than any other Van-patterned cat, nor will they have a higher risk for any other disease. A Van-patterned Turkish Van, even if it has all-white ancestors on its pedigree, does not carry the dominant white gene, which means it can never have all-white offspring unless mated to an all-white Turkish Van. Anyone not wishing to work with all-white Turkish Vans should simply not acquire any. Using all-white Turkish Vans for the Turkish Van breeding program, will not lead to an increase of under- or over marked Turkish Vans. The dominant white gene will have no effect on the amount of spotting in a patterned cat, except to mask the pattern.
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