Genetic Testing In Breeds

Topic: Genetic Conditions in Dogs

Filed under Dogs

Tags: Genetics, Progressive Retinal Atrophy, Narcolepsy, Collie Eye Anomaly, DNA

 

There are several specific genetic testing services that cater specifically to breeders, owners and veterinarians. Genetic testing is often done in pedigree and championship breeding programs as it is one of the only ways to determine if a dog may be a carrier of recessive genetic problems. Of course these recessive genetic issues will eventually become known once the dog is bred, however with some conditions and with the right breeding mate it may be many litters before the problem is noticed.

Recessive genes have long been the problem with many of the current health conditions commonly seen in different breed lines. Recessive genes only show their trait, the health problem, if both of the parent dogs had the recessive gene and both passed that particular gene on during fertilization of the egg. When only one dog has the recessive gene or if both dogs have the recessive gene but it isn't used in that particular gene pairing, the offspring will be known as carriers. This means they have the bad gene but it is not going to cause any health issues for that dog since they only have one, not two.

Most recessive genetic problems occur with just one gene pair. However there are some conditions, such as hip dysplasia, that are considered polygenic, which means there is more than one genetic combination that can produce the condition or that is required to cause the animal to have the symptoms. Needless to say the more combinations or possibilities of a genetic mismatch causing a condition the more likelihood that any offspring from that particular dog or breeding combination will have the genetic condition.

Testing in advance of breeding for the many of the very serious and some of the less serious genetic problems is not always necessary, especially if there is a well recorded health history for each dog in the pair that goes back several generations. Recessive genes and some conditions can skip generations, but they usually will be seen somewhere in the line within three to four generations if they are present. There are still abnormal genes or genetic mutations that may occur, but these are actually relatively rare and usually result in very significant malformations and health issues within the litter.

It is also unnecessary to have dogs tested for specific conditions that are not found within the breed. For example, most large dogs need to be tested for hip dysplasia that can be certified free from the condition once the dog is fully mature. This test can be repeated since it is more common to see the problem develop later in life. In a small or toy breed where hip dysplasia is not a problem, unless there was some specific concern or history in a particular breeding line testing for this condition would not be required.

A great number of breeds have the same type of problematic autosomal recessive genetic condition, which then can be tested for with simple blood tests. PRA or progressive retinal atrophy, a condition that is painless but causes dogs to gradually go completely blind, is one disease that can be tested for prior to breeding. This is important since it normally doesn't occur until the dog are middle aged, meaning they may have already passed the trait on to many litters of puppies.

Interesting enough, narcolepsy is a fairly common neurological condition seen in several breeds. Labs, Dobermans and even the low bodied Dachshunds may be prone to this sleeping disorder. Genetic testing can identify females and males that are carriers of the condition prior to breeding to avoid breeding two carriers together.

Most collie breeds and some of the sheep herding breeds have a breed specific condition known as Collie Eye Anomaly or CEA. This is a lesion that occurs in the choroid under the retina, causing mild to significant vision problems. While it is often seen in very young puppies, the dogs will adjust with just mild symptoms, often leading the owners to mistakenly believe the situation has corrected itself. Dogs that have CEA or are carriers of the gene will pass this potentially serious condition on to their offspring. Testing in advance of breeding in any collie breed or collie cross is highly recommended to prevent this genetic problem from increasing in frequency.

Besides just testing for disease and problem genes, DNA or genetic testing can also be used by breeders to make more accurate breeding matches to breed puppies with specific coat colors and types. This is important for those breeds that offer a variety of coat colors and even coat patterns as some of the merle, brindle and even tri-colored coats are more sought after. In breeds where there are different coat types from short to long, gene testing can also help determine which two parents will produce more of the longer or shorter coats, depending on what the breeder is after.

Finally, just like in horse and cattle breeding, more and more purebred breeders are having their championship male and female dogs DNA tested and typed so that they can authenticate any litters from the champion line. In the past, and more commonly in the highly popular breeds, there has been a concern expressed that often puppy mills and puppy farms were claiming that specific dogs were used in their breeding, when in fact the paperwork was not authentic or the dog is not really the male used in the cross. DNA samples that are certified and recorded through the different DNA labs and companies provide a lasting record of the actual DNA of each dog, allowing breeders to verify and confirm as well as discount misleading registration and pedigree paperwork.

DNA testing is still relatively new in canine medicine, however there are several research organizations and veterinarians that are striving to make headway into the problematic genetic conditions found in dogs and other types of domestic animals. This information will definitely help eliminate recessive genetic problems in the dogs of the future, plus it will help breeders choose the best possible combinations to enhance and improve future of their breed.

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