Progressive Retinal Atrophy (PRA) is primarily an autosomal recessive genetic disorder in most breeds.
Understanding PRA Inheritance
PRA is an inherited condition affecting the eyes of certain dog breeds and cats. It leads to the degeneration of the retina, eventually causing blindness. As the provided reference states:
- PRA is an inherited trait.
- It is autosomal recessive in most breeds.
This means the gene responsible for PRA is located on an autosome (a non-sex chromosome) and that an animal must inherit two copies of the mutated gene – one from each parent – to develop the condition.
What Does Autosomal Recessive Mean?
In simple terms, here’s what autosomal recessive inheritance typically involves:
- Affected: An animal needs two copies of the abnormal gene (let's call the mutated gene 'p' and the normal gene 'P'). An affected animal has the genotype 'pp'.
- Carrier: An animal that inherits only one copy of the abnormal gene ('Pp'). Carriers usually do not show symptoms of PRA but can pass the gene on to their offspring.
- Clear: An animal that inherits two copies of the normal gene ('PP'). They are unaffected and cannot pass on the abnormal gene.
This inheritance pattern explains why two parents who appear healthy (carriers) can produce affected offspring.
Implications of Recessive Inheritance
Understanding that PRA is generally autosomal recessive is crucial for breeders and owners:
- Genetic Testing: DNA tests are available for many forms of PRA, allowing owners and breeders to identify affected, carrier, and clear animals.
- Breeding Decisions: Knowledge of a dog's genetic status allows for informed breeding choices to reduce the incidence of the disease in future generations. Breeding two carriers, for example, carries a risk of producing affected puppies.
- Carrier Status: Identifying carriers is important because they can pass the condition on even if they show no signs themselves.
| Genetic Status | Genotype | Passes Mutated Gene | Shows Symptoms (Typically) |
|---|---|---|---|
| Clear | PP | No | No |
| Carrier | Pp | Yes | No |
| Affected | pp | Yes | Yes |
Note: While PRA is primarily autosomal recessive, some rarer dominant or X-linked forms exist in specific breeds, but the most common forms are recessive.
Knowing the mode of inheritance helps manage genetic health within animal populations.
