What causes a deafness and blindness in dogs?

Con't on the Merle Gene and how it effects deafness and blindness in dogs. Remember Merle causes whitening and its the whitening that causes defects.

For now, we will leave behind the Mm dog and mm dog, and focus more on the MM dog, also known as the homozygous merle.

So lets take our imaginary Sire and Dam. Let's just say, the dam gives us one of her genes(she does not have a say at this it's all how the cookie crumbles), then the sire gives us one of his. Let's give our genes a value, and those are M and m in this case. "M" being the dominant gene, and "m" being the recessive gene.

Now, lets make two piles. A winning pile, that will comprise of what the dog looks like outside/externally, and the loosing pile that will be in the inside of the dog, that the dog carries. The dominant gene will go on, while the recessive gene gets thrown back into the unborn puppy. It could also happen that we have a tie... and both genes are either dominant or recessive, and its anyone guess who's gene the sire or the dam the puppy gets. Keep in mind we are just talking about the Merle gene (as in the pattern), but there are hundreds of genes that make up the complete dog of course.

So in this case, every time a M gene is given off by sire or damn its going to move on, because its a dominant gene. Therefore you will have a merle puppy. Once this puppy is and adult and ready to have his/her own puppies, the dominant and recessive genes get shuffled and the game begins again.

It's all about likelihood. Even though the gene pool is going to get shuffled, a merle sire and a merle dam should not be breed together. It is very likely that this will result in double merles because they both have an equal chance of passing the dominant merle gene. And if this happens, what actually goes on is this... lets say the sire's dominant gene goes off and starts patterning the puppy's tail white but does not touch any other part of the body. The damn's dominant gene goes off and starts patterning the puppy's body, and then goes to the tail, and adds more white to it. Now you have a marbled look body and a completely white tail. It is this "double touching" that is lethal and presents issues such as deafness and blindness in dogs. Very rarely does a double merle dog get away from medical, health problems.... but it could happen.

If in this breeding program, the sire and damn both draw the recessive gene m, then there it finally has the chance to win, but if it is paired with a M, it would have to wait until the next time to breed and try again. In the meantime, breeders who lack this knowledge (and this by no means is extensive), are the ones who people should not buy from. It is as a result of their lack of understanding, concern and care for the betterment of breeds, that they develop "faulty" dogs.... based on trial and error. Puppy mills and back yard breeders go into this category too.

Remember Merle causes whitening and its the whitening that causes defects.

Dog Responsibly....University of Doglando

Dog Responsibly....University of Doglando