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Dominant PRA Test:

For: (Old English) Mastiff and Bullmastiff

Background information on this disease and on the research leading up to this genetic test is given on the Mastiff Club of America web site.

 You can send in blood samples for testing by following the directions at the "Ship Sample" link and completing the "Request Test" form available at that  link. The price of the Dominant PRA test for Mastiffs and Bullmastiffs is $120 per dog. The typical turn-around time from receipt of the blood sample to report of results is about 2 weeks.

Since vision loss might be recognized first when the dog is several years old, it’s important to determine the actual status of the dog before breeding it. The Mastiff Club of America (MCOA) states “PRA has been found during Mastiff eye exams as early as four months and there are Mastiffs that have CERFed as normal at three years and been found to have PRA before they turned four years old.” Since the same gene and mutation cause PRA in both (English) Mastiffs and Bullmastiffs, the same test is used for both. The Dominant PRA test for Mastiffs and Bullmastiffs detects the actual mutation in the PRA disease gene. The test can be done at any age – from pup to adult, including prior to any vision loss, and the result will never change with age.

Mastiffs and Bullmastiffs exhibit the first, and so far, only form of canine Progressive Retinal Atrophy – PRA - that is dominantly inherited. This means a single copy of the mutant gene causes the disease, in contrast to two copies required in a recessive disease. (Remember - one copy of every gene is passed to the offspring from the dam and one from the sire.) There are no “carriers” of dominant PRA; dogs are either normal or affected.

It is IMPORTANT to note that dogs that are affected with Dominant PRA are very susceptible to additional retinal damage when exposed to bright light.  For this reason, dogs should not have ophthalmological exams unless the doctor is using an infrared apparatus.  Also, conditions such as bright sunshine or bright indoor lighting should be avoided. This will help to prevent significant light damage that is associated with this disease.


The OptiGen test results for Dominant PRA will be reported as follows:

  • Homozygous Normal – this dog is not and will not become affected with PRA. It has two normal PRA gene copies and will pass along only the normal gene to its offspring.

  • Heterozygous Affected – this dog is or will be affected with PRA. It has one dominant PRA mutant gene copy and one normal gene copy. On average, half of its offspring will receive the mutant gene copy and half of its offspring will receive the normal gene copy.

  • Homozygous Affected – this dog is or will be affected with PRA. It has two dominant PRA mutant gene copies and no normal gene copies. All of its offspring will receive the mutant gene causing PRA.

Testing gives breeders a new genetic advantage. Based on test results, disease can be prevented with certainty. In the case of dominant disease, the mutant gene can be eliminated rapidly. This requires exclusion of the affected dog from further breedings. The MCOA states at its web site “Mastiffs with PRA should not be bred.” That might seem to be an impossible solution for some breeders, but then the consequences must be considered. The following table gives the possible breeding combinations and their outcomes.


NOTE: N designates the Normal gene copy
            D designates the Dominant Mutant gene copy

Expected results for breeding strategies using the
OptiGen mutation test for Mastiff and Bullmastiff Dominant PRA
Parent 1
Genotype
Parent 2     Genotype
Homozygous
Normal
NN
Heterozygous
Affected
ND
Homozygous
Affected
DD
Homozygous Normal
NN
All Normal = NN 1/2 Normal = NN
1/2 Hetero. Affect. = ND
All Hetero. Affect. = ND
Heterozygous Affected
ND
1/2 Normal = NN
1/2 Hetero. Affect. = ND
1/4 Normal = NN
1/2 Hetero. Affect. = ND
1/4 Homozyg. Affect. = DD
1/2 Hetero. Affect. = ND
1/2 Homozyg. Affect. = DD
Homozygous Affected
DD
All Hetero. Affect. = ND
1/2 Hetero. Affect. = ND
1/2 Homozyg.Affect. = DD
All Homozyg.Affect. = DD

The research leading to this discovery was undertaken by scientists at the James A. Baker Institute of Animal Health at Cornell University's College of Veterinary Medicine in Ithaca, New York, and published in volume 99 of the April 2002 issue of the Proceedings of the National Academy of Sciences. The technology underlying this test is done by agreement with Cornell Research Foundation, Inc. PCR technology is performed under a license agreement with Roche Molecular Systems, Inc.

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OptiGen®, LLC · Cornell Business & Technology Park · 767 Warren Road, Suite 300 · Ithaca, New York 14850
Tel: 607 257 0301 · Fax: 607 257 0353 · email: genetest@optigen.com or optigen@clarityconnect.com
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