NOVA SCOTIA DUCK TOLLING RETRIEVER

In the case of PRA, also keep in mind that not all retinal disease is PRA and not all PRA is the form currently detectable in your breed. Accurate diagnosis is essential. A dog can test as normal or carrier, yet be affected by a different type of PRA. Although more than one type of retinal degeneration probably occurs in every breed, by far the most common type of PRA for your breed is the type currently being tested by OptiGen.

Possible results using the OptiGen prcd test

Pattern/Genotype* Risk Group Significance For Breeding Risk For Developing prcd

                     A I. Normal Can be bred to any dog,
with 99.5% confidence of
producing no affected pups Not expected to develop prcd, risk is less than 0.0025%

                     B II. Nonaffected Probably a carrier of prcd
(99.0% confidence)and
should be bred only to
Pattern A Not expected to
develop prcd, risk is
less than 0.5%

                     C III. High Risk Probably homozygous for
prcd(99.5% confidence)and should be
bred only to Pattern A Probably will develop
prcd, with only 0.5%
chance of not being
affected.

* Probability risks are based on estimated frequency of recombination between the prcd
markers and the disease gene.

The next table shows that all the desirable breedings include at least one parent
with Pattern A genotype from the OptiGen prcd test. All other breedings are at
risk of producing pups of Pattern C, with a high probability of developing prcd.
However, all dogs can be bred with a high degree of safety. It isn't necessary - or
even desirable - to remove dogs from the breeding population. But when
choosing pups to retain as potential breeding stock, it is important to select for
dogs with Pattern A genotype - and select against dogs with Pattern C genotype.

Expected results for breeding strategies using the OptiGen prcd test
                                                                                                        Parent 2     Genotype

Parent 1
         Genotype                    A                       B                        C

                    A All = Pattern A 1/2 = Pattern A
                 1/2 = Pattern B All = Pattern B

                    B 1/2 = Pattern A
                    1/2 = Pattern B 1/4 = Pattern A
         1/2 = Pattern B
                  1/4 = Pattern C 1/2 = Pattern B
                 1/2 = Pattern C

                    C All = Pattern B 1/2 = Pattern B
                 1/2 = Pattern C All = Pattern C

Add. to this list - to:my.skold @ bredband.net

July 27, 2007

*Expected results for breeding strategies using the OptiGen prcd* test**
Parent 1 Status	Parent 2 Status
Parent 1 Status	Normal/Clear	Carrier	Affected
Normal/Clear	All = Normal/Clear	1/2 = Normal/Clear 1/2 = Carrier	All = Carrier
Carrier	1/2 = Normal/Clear 1/2 = Carrier	1/4 = Normal/Clear 1/2 = Carrier 1/4 = Affected	1/2 = Carrier 1/2 = Affected
Affected	All = Carrier	1/2 = Carrier 1/2 = Affected	All = Affected

Pattern/Genotype*	Risk Group	Significance For Breeding	Risk For Developing prcd
A	I. Normal	Can be bred to any dog, with 99.5% confidence of producing no affected pups	Not expected to develop prcd, risk is less than 0.0025%
B	II. Nonaffected	Probably a carrier of prcd (99.0% confidence)and should be bred only to Pattern A	Not expected to develop prcd, risk is less than 0.5%
C	III. High Risk	Probably homozygous for prcd(99.5% confidence)and should be bred only to Pattern A	Probably will develop prcd, with only 0.5% chance of not being affected.

Parent 1 Genotype	A	B	C
A	All = Pattern A	1/2 = Pattern A 1/2 = Pattern B	All = Pattern B
B	1/2 = Pattern A 1/2 = Pattern B	1/4 = Pattern A 1/2 = Pattern B 1/4 = Pattern C	1/2 = Pattern B 1/2 = Pattern C
C	All = Pattern B	1/2 = Pattern B 1/2 = Pattern C	All = Pattern C