PRA iN DOGS

We have inserted this page to explain to people important information on PRA in dogs as so many people have heard about this condition and ask about it but do not understand what the results mean, we hope you find this useful.

Trait of Inheritance

The mutation in the PRCD gene which has been suggested to cause prcd-PRA has recently been published by the group of Gustavo D. Aguirre at the University of Pennsylvania, USA, and could be found in several dog breeds. Prcd-PRA is inherited as an autosomal recessive trait. So there are three conditions a dog can be: it can be clear (genotype N/N or homozygous normal) meaning that it does not carry the mutation and will not develop the prcd-form of PRA. Since it also cannot pass the mutation onto its offspring, it can be mated to any other dog.
A dog which has one copy of the PRCD gene with the mutation and one copy without the mutation is called a carrier or heterozygous (genotype N/PRA); while it will not be affected by prcd-PRA, it can pass the mutation onto its offspring and should therefore only be mated to clear dogs. Dogs that develop this form of PRA have two PRCD gene copies with the mutation (genotype PRA/PRA or homozygous affected); they will always pass the mutated gene onto their offspring and should also be mated only to clear dogs..

 Inheritance : AUTOSOMAL RECESSIVE trait

 SIRE DAM OFFSPRING
 
Clear x Clear > 100% Clear
 
Clear x Carrier > 50% Clear + 50% Carriers
 
Clear x Affected > 100% Carriers
 
Carrier x Clear > 50% Clear + 50% Carriers
 
Carrier x Carrier > 25% Clear + 25% Affected + 50% Carriers
 
Carrier x Affected > 50% Carriers + 50% Affected
 
Affected x Clear > 100% Carriers
 
Affected x Carrier > 50% Carriers + 50% Affected
 
Affected x Affected > 100% Affected

CLEAR

Genotype: N / N [ Homozygous normal ]

The dog is noncarrier of the mutant gene.

The dog will never develop prcd - PRA ( Progressive Retinal Atrophy ) and therefore it can be bred to any other dog.
 

CARRIER

Genotype: N / PRA [ Heterozygous ]

The dog carries one copy of the mutant gene and one copy of the normal gene.

The dog will never develop prcd - PRA ( Progressive Retinal Atrophy ) but since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%.
Carriers should only be bred to clear dogs.

Avoid breeding carrier to carrier because 25% of their offspring is expected to be affected (see table above)

AFFECTED

Genotype: PRA / PRA [ Homozygous mutant ]

The dog carries two copies of the mutant gene and therefore it will pass the mutant gene to its entire offspring.

The dog will develop prcd - PRA ( Progressive Retinal Atrophy ) and will pass the mutant gene to its entire offspring

This is so complicated. Can't you give me "Just the Facts"?

OptiGen prcd-PRA testing in LRs, ECSs, CBRs, PWDs, Poodles, ACDs, Tollers, and Eskies: This test....identifies Pattern A = clear/normal and the result is almost 100% accurate. Identifies Pattern B = probably a carrier, but could be clear. NOT affected. Identifies Pattern C = at high risk of being either affected or a carrier, with very low chance of being clinically clear/normal. Does not definitively identify carriers or affecteds. Can be done at any age, and would be repeated only for Bs and Cs when an improved test is available. This means…Pattern A result is not limited by the false allele. Pattern B and C uncertainties are due to the test detecting a false allele. Pattern C dogs older than the typical age of diagnosis and with clinically normal vision are most probably a carrier, or less likely, a clear/normal. Pattern A, B or C reflects a set of DNA markers. They will never change unless the test is revised. The Pattern will always remain the same and be passed on to offspring. You now can… avoid producing affected pups by breeding Pattern B or C to Pattern A. Eliminate prcd-PRA disease from the breed. Safely keep Pattern B or C dogs in your breeding program. Eliminate ERG’s to test for prcd-PRA disease in Pattern A and B dogs. Please note…there is no estimate of the frequency of the false allele at this time, although it is much lower with the recently improved tests. Researchers are working hard to identify the actual gene mutation and remove the uncertainties of the B and C