Sire		Dam		Offspring
clear		clear		100% clear
clear		carrier		50%  clear + 50% carriers
clear		affected		100% carriers
carrier		clear		50%  clear + 50% carriers
carrier		carrier		25% clear + 25% affected + 50% carriers
carrier		affected		50% carriers + 50% affected
affected		clear		100%  carriers
affected		carrier		50% carriers + 50% affected
affected		affected		100% affected

Clear

Genotype: N / N [ Homozygous normal ]

The dog is noncarrier of the mutant gene.

It is very unlikely that the dog will develop Progressive Retinal Atrophy ( PRA4 ). The dog will never pass the mutation to its offspring, and therefore it can be bred to any other dog.

 

Carrier

Genotype: N / PRA4 [ Heterozygous ]

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

It is very unlikely that the dog will develop Progressive Retinal Atrophy ( PRA4 ) 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: PRA4 / PRA4 [ 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 is likely to develop Progressive Retinal Atrophy ( PRA4 ) and will pass the mutant gene to its entire offspring