The Kennel Club has approved two new official DNA test reporting schemes for X-linked progressive retinal atrophy 1 (XLPRA1) and X-linked hereditary nephritis (XLHN) in Samoyeds, following consultation with the breed’s health co-ordinator on behalf of the breed clubs.
XLPRA1
XLPRA1 is an inherited condition that causes problems with the retina (a layer of light-sensitive tissue at the back of the eye). The retina contains special cells, called photoreceptors, that play a vital role in vision. In affected dogs, their photoreceptors begin to break down, causing vision problems that gradually become worse, sometimes leading to total blindness. Some individuals may be more affected than others.
The disease is described as X-linked, which means that the faulty gene that causes this type of PRA is found on the X-chromosome. The X-chromosome helps to determine a dog’s sex.
Male dogs only have one X-chromosome, which they always inherit from their mother, while females have two X-chromosomes, which they inherit from both their mother and father.
In females, the disease acts in a recessive way, i.e., a female must inherit two copies of the faulty gene (one from her mother and one from her father) to be affected.
In males, because they only have a single copy of the X-chromosome, the condition behaves as if it were dominant and male dogs are either healthy (they only have a healthy copy of the gene) or affected (they only have the faulty copy of a gene).
Tested dogs will be recorded on The Kennel Club systems as either:
- Clear - If your dog is clear, they will not have any copies of the faulty gene associated with XL-PRA1 and will only pass on a normal copy of the gene to any offspring.
- Carrier - Carriers have one healthy and one faulty version of the gene associated with XL-PRA1. Only females can have two copies of the X chromosome, and so only females can be carriers for XL-PRA1. Despite carrying one copy of the faulty gene, the dog is unlikely to be affected by the condition. When bred from, a carrier has a 50 per cent chance of passing the faulty gene on to her puppies.
- Affected - A female with two copies of the faulty genes, one inherited from her mother and one from her father, will be affected. An affected male will have a single copy of the faulty gene, which he inherited from his mother.
If bred from, affected females will pass on a copy of this abnormal gene to all their offspring. Any male puppies that inherit the faulty gene will be affected.
Affected males will pass this faulty gene on to all female puppies, but not to male puppies.
XLHN
XLHN is an inherited condition that causes certain parts of a dog’s kidneys to become inflamed and stop working correctly. In males, and some females, this progresses to kidney failure and death, often at a young age.
The disease is described as X-linked, which means that the faulty gene that causes this type of nephritis is found on the X-chromosome. The X-chromosome helps to determine a dog’s sex.
Male dogs only have one X-chromosome, which they always inherit from their mother, while females have two X-chromosomes, which they inherit from both their mother and father. In females, the disease acts as an incomplete dominant trait, i.e., if a female is a carrier (has one faulty and one healthy copy of the gene), her health is going to be affected, but not as severely as if both copies of the gene she carries are faulty. In males, because they only have a single copy of the X-chromosome, the condition is dominant and they are either healthy (they only have a healthy copy of the gene), or severely affected (they only have the faulty copy of a gene).
Tested dogs will be recorded on The Kennel Club systems as either:
- Clear - If your dog is clear, they will not have any copies of the faulty gene associated with X-linked nephritis and will only pass on a normal copy of the gene to any offspring.
- Single affected - A single affected male will have one copy of the faulty gene, which he inherited from his mother. These dogs are likely to be severely affected by the disorder. If bred from, single affected males will pass a copy of this abnormal gene to all female puppies, causing them to become affected. They will not pass the abnormal gene to their male puppies.
Females can have two copies of the X-chromosome. A single affected female will have one healthy and one faulty version of the gene associated with X-linked nephritis. The dog is likely to be affected by the condition, although the severity varies between individuals. When bred from, a single affected female has a 50 per cent chance of passing the faulty gene to each of her puppies and so can produce affected puppies.
- Double affected - A double affected female has two copies of the faulty genes, one inherited from her mother and one from her father. These dogs are likely to be severely affected by the disorder. If bred from, double affected females will pass on a copy of this abnormal gene to all of their offspring and so will produce affected puppies.
To find out more on The Kennel Club’s breeding advice for these DNA tests and to find out which laboratories The Kennel Club records results from, please refer to The Kennel Club website page about XLPRA1 and XLHN. Please note that these listings are not necessarily comprehensive and other labs may offer the tests. To find out which DNA tests are relevant to your breed, visit The Kennel Club's Breeds A-Z.
Please note that due to the way that these conditions are inherited, and the way that The Kennel Club database currently works, The Kennel Club is not able to record the hereditary status of puppies that are born from two tested dogs.
The Kennel Club constantly reviews DNA testing schemes in conjunction with breed clubs to ensure that breeders are supported with resources which help them to make responsible breeding decisions. The Kennel Club works alongside breed clubs and breed health co-ordinators in a collaborative effort to improve the health of pedigree dogs and is happy to consider a club's request to add a new DNA test to its lists. A formal request from the breed's health co-ordinator or a majority request from the breed clubs is normally required to do this.
Test results will be added to the dog’s registration details which will trigger the publication of the result in the next available Breed Records Supplement and also on the Health Test Results Finder on The Kennel Club website.
Results for dogs already tested can also be recorded, but owners will need to submit copies of the DNA certificates themselves. DNA test certificates should be scanned and emailed to
Health results (The Kennel Club) .
Owners are reminded that from August 2018, the dog’s microchip (or tattoo) must be recorded along with either the dog’s registered name or registered number on any DNA certificates. Any test results issued after that date that do not carry these identifying features will not be accepted.