Genetic diseases in dogs have been with us for a long time. In fact, they probably started when dogs evolved mony millenia ago. Because dogs are biologic mechanisms, as are people and all other living things, they are subject to mutations. As a general rule, mutations are negative, that is, they tend to alter some characteristics of the dog that make the animal less able to weather variations in the enviroment. Some mutations occur in various tissues of the body but do not involve the reproductive cells. These are called SOMATIC MUTATIONS. They may do harm to the body - for instance, cause a cancer to develop - but are not passed on to the next generation.
While in general, mutations are harmful, they are clearly not all harmful, some mutations, were selected for by the early breeders, hundreds of years ago, perhps even thousands of years ago. While we do not know for certain what type of coat the original dog had, we now know there are many variations available genetically, such as wavy, curly, wiry, long, short and even no coat as can be seen in the Chinese Crested. Some of these coat variations were used as a basis for a breed, such as the German Wire-haired dachshund or curly-coated retrievers, although they are not the only basis for these breeds. No matter what is thought about coats in general, it is known the original dogs could not have all these variations. So over the years, mutations occured in the coat genes, causing the variations that we see today. Breeders then selected for coat types they liked and stabilised them by inbreeding to form the more or less uniform coats we see today. The same things happened with eye colour, ear type, coat colour, height, weight and all the other characteristics that allow us to distinguish one breed from another and that distinguish each breeed from the original dog, however the original dog may have looked. In other words these are collections of beneficial mutations that breeders put together and stabilized to form the 400 or 500 distinct breeds known in the world tody.
Sometimes it is easy to tell whether a condition is genetic, but at other times, especiially if there are only one or two cases, it is very difficult to determine whether it is or not and in the final analysis you may not be able to state with certainty that a trait is genetic in origin. For traits that repeatedly occur within a breed the first question to ask is 'is it familial?'. While htere are many situations in which a disorder occurs in multiple members of a litter, in most instances, ths disoprder will not recur in spaced litters unless it is genetic. Genetic traits must follow family lines, and they do occur in multiple, widely-spaced litters. So if a defect occurs among the dogs in your kennel or breeding lines, you must sure the diagnosis is accurate.
If the defect is inhereited in dogs or in other species, then the chances that it is inherited in the affected dogs in your kennel are good. There are of course, PHENOCOPIES - traits that are known to be genetic, but can also be produced by something in the enviroment that tend to confusse the situation. Cleft plate, a defect that occurs in nearly all breeds, is an example of a trait in which phenocopies occur. There are 22 compounds known to cause clweft palate. One of these is an excess of Vitamin A. Other examples are anti-inflammatory drugs like prednisone or prenisolone. If these drugs are given on days 18 through to 21 or are carried over in the body from a slightly earlier treatment, they can cause cleft palate. A trait that occurs in your breed or your breeding lines should be considered to be inherited in your dog unless proven otherwise. Ask yourself whether the MODE of inheritance of the trait is known in your breed, in other breeds or in other species. IOther factors that can cause genetic defects to raise their ugly heads in your dogs athat must be considered are -
If you cant prove that any of the above cause the trait, problems begin to arise. Here is where a veterinarians 'famous' advice to breeders comes into play. 'Dont worry about it - outcross and even if it is genetic, it will go away'. It is this famous advice that has messed up breeds of dogs from time immemorial. Instead of controlling a trait when there are noe or two dogs or one or two families involved, the dogs have been outcrossed and spread the trait throughout the breed.
To prevent serious genetic diseases in dogs, both in pedigrees and crossbreeds, you only need three things to accomplish this task - KNOWLEDGE INFORMATION & HONESTY.
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