Why is DNA testing significant?
Why is DNA testing significant?
In our program, we have chosen to test for: Patella Luxation, Cardiac Disease, Juvenile Hereditary Cataracts, Degenerative Myelopathy, Canine Multifocal Retinopathy, Hypoplastic Trachea and Hemivertebrae. We also test our male stud dogs for Progressive Retinal Atrophy and Hyperuricosuria. We have discussed patella luxation, hemivertebrae, hypoplastic trachea and cardiac disease on the OFA Information page. Please refer to that page for more information on those topics.
Juvenile Hereditary Cataracts (JHC)
Cataracts are a clouding of the lens of the eye caused by a breakdown of tissue in the eye. This generally results in an inability to see clearly, and can cause total blindness. In canines, cataracts are often familial; this type is known as Hereditary Cataracts. A mutation in the HSF4 gene causes this type of cataracts in several breeds of dogs. In this case, the dog is typically affected in both eyes. The cataracts associated with HSF4 also can occur in the posterior region of the lens. They usually begin small and grow with time, though the speed of growth is highly variable. Some cataracts will grow so slowly that the dog's vision remains relatively clear, while others grow such that the dog will quickly go blind. Corrective surgery is possible, though it is costly and it not always effective.
One HSF4 mutation causes the recessive form of Hereditary Cataracts in Boston Terriers, Staffordshire Bull Terriers, and French Bulldogs. Because it is recessive, a dog must have two copies of this mutation to experience this form of cataracts. This mutation is responsible for early onset Hereditary Cataracts, which typically occurs between 12 months and 3 years.
It should be noted that not all cataracts are hereditary. Cataracts can also be caused by old age or injury.
(Animal Genetics Incorporated offers DNA testing and detection of the gene mutation responsible for the genetic form of Hereditary Cataracts.)
Results are given as follows:
JHC/JHC (Affected): The dog carries two copies of the mutant gene and is homozygous for Hereditary Cataracts. The dog is affected and will always pass on a copy of the mutant gene to its offspring. THESE DOGS SHOULD NOT BE BRED.
n/JHC (Not Affected/Carrier): Both the normal and mutant copies of the gene detected. Dog is a carrier for Hereditary Cataracts, and can pass on a copy of the defective gene to any offspring. THESE DOGS SHOULD ONLY BE BRED TO CLEAR DOGS.
n/n (Not Affected/Clear): Dog tested negative for the Hereditary Cataract gene mutation, and will not pass on the defective gene to its offspring. CANDIDATE FOR BREEDING.
Degenerative Myelopathy (DM)
Degenerative Myelopathy (DM) is a progressive neurological disorder that affects the spinal cord of dogs. Dogs that have inherited two defective copies will experience a breakdown of the cells responsible for sending and receiving signals from the brain, resulting in neurological symptoms.
The disease often begins with an unsteady gait, and the dog may wobble when they attempt to walk. As the disease progresses, the dog's hind legs will weaken and eventually the dog will be unable to walk at all. Degenerative Myelopathy moves up the body, so if the disease is allowed to progress, the dog will eventually be unable to hold his bladder and will lose normal function in its front legs. Fortunately, there is no direct pain associated with Degenerative Myelopathy.
The onset of Degenerative Myelopathy generally occurs later in life starting at an average age of about 8 years. However, some dogs may begin experiencing symptoms much earlier, some later, and a small percentage of dogs that have inherited two copies of the mutation will not experience symptoms at all. Thus, this disease is not completely penetrant, meaning that while a dog with the mutation is highly likely to develop Degenerative Myelopathy, the disease does not affect every dog that has the genotype.
This disease can affect any breed. Recently, a surprising number of bulldogs have been diagnosed with Degenerative Myelopathy. It is very important to have your breeding stock tested.
(Animal Genetics Incorporated offers DNA testing and detection of the gene mutation responsible for the genetic form of Hereditary Cataracts.)
Results are given as follows:
DM/DM (Affected): The dog carries two copies of the mutant gene and is homozygous for Degenerative Myelopathy. The dog is affected and will always pass on a copy of the mutant gene to its offspring. THESE DOGS SHOULD NOT BE BRED.
DM/n (Not Affected/Carrier): Both the normal and mutant copies of the gene detected. Dog is a carrier for Degenerative Myelopathy, and can pass on a copy of the defective gene to any offspring. THESE DOGS SHOULD ONLY BE BRED TO CLEAR DOGS.
n/n (Not Affected/Clear): Dog tested negative for the Degenerative Myelopahty gene mutation, and will not pass on the defective gene to its offspring. CANDIDATE FOR BREEDING.
Canine Multifocal Retinopathy (CMR1)
Canine Multifocal Retinopathy (CMR) is an autosomal recessive eye disorder.
The mutation causes raised lesions to form on the retina which alters the appearance of the eye but usually does not affect sight. The lesions may disappear, or may result in minor retinal folding. Symptoms of the mutation usually appear when a puppy is only a few months old, and generally do not worsen over time.
CMR is recessive, so both parents would need to be carriers of the mutation to produce an affected puppy. "Clear" CMR dogs do not carry the mutation for the disorder. Breeding two clears or one clear and one carrier will not produce affected offspring, however if one parent is a carrier, a percentage of the offspring will be carriers. Therefore, it is useful to test for the presence of the CMR mutation before breeding. Additionally, since retinal defects can be caused by other conditions, testing can verify that a dog actually has CMR rather than some other eye condition.
(Animal Genetics Incorporated offers DNA testing and detection of the gene mutation responsible for the genetic form of Canine Multifocal Retinopathy.)
Results are given as follows:
CMR/CMR (Affected): The dog carries two copies of the mutant gene and is homozygous for Canine Multifocal Retinopathy. The dog is affected and will always pass on a copy of the mutant gene to its offspring. THESE DOGS SHOULD NOT BE BRED.
CMR/n (Not Affected/Carrier): Both the normal and mutant copies of the gene detected. Dog is a carrier for Canine Multifocal Retinopaathy, and can pass on a copy of the defective gene to any offspring. THESE DOGS SHOULD ONLY BE BRED TO CLEAR DOGS.
n/n (Not Affected/Clear): Dog tested negative for the Canine Mulltifocal Retinopathy gene mutation, and will not pass on the defective gene to its offspring. CANDIDATE FOR BREEDING.
Hyperuricosuria (HUU)
Dogs with this genetic mutation metabolize waste products as uric acid in their urine. The uric acid forms into hard stones in the bladder, causing pain and inflammation as the stone moves through the urinary tract.
A dog that has difficulty urinating or appears to have an inflamed bladder may have HUU. Other signs can include blood in the urine and frequent urination. If the dog is unable to pass the urate stones without medical intervention, surgery may be required to remove them. And if the urinary tract is blocked, the condition can be life threatening. Even in the best case scenario, HUU is uncomfortable and painful for the dog.
The mutation is autosomal recessive. Both parents will need to be carriers of the mutation to pass it on to their offspring. Carriers will not show any symptoms of HUU and even affected dogs may not show any signs, so it is important to test dogs for HUU prior to breeding.
(Animal Genetics Incorporated offers DNA testing and detection of the gene mutation responsible for the genetic form of Hyperuricosuria.)
Results are given as follows:
HUU/HUU (Affected): The dog carries two copies of the mutant gene and is homozygous for Hyperuricosuria. The dog is affected and will always pass on a copy of the mutant gene to its offspring. THESE DOGS SHOULD NOT BE BRED.
HUU/n (Not Affected/Carrier): Both the normal and mutant copies of the gene detected. Dog is a carrier for Hyperuricosuria, and can pass on a copy of the defective gene to any offspring. THESE DOGS SHOULD ONLY BE BRED TO CLEAR DOGS.
n/n (Not Affected/Clear): Dog tested negative for the Hyperuricosuria gene mutation, and will not pass on the defective gene to its offspring. CANDIDATE FOR BREEDING.
