In recessive genetic pathologies, for the disease to develop, the presence of both diseased alleles is necessary (transmitted by both parents, from the father and mother), so there are clinically normal animals that can be carriers of a diseased allele "occult" (transmitted by only one of its parents).

With DNA analysis, which allows the genotype of the animals to be identified, the mutation can be detected even before the disease has manifested, or in the cases of carrier dogs.

Late onset ataxia LOA is an inherited disease caused by a mutation in the CAPN1 gene. This pathology is specific to the Jack Russell Terrier and the Parson Russell Terrier.

Dogs affected by this disease begin to show the first symptoms between 6 and 12 months of age. The first clinical signs are loss of balance and a slight lack of coordination of gait, later symptoms are progressive lack of coordination, difficulty standing and even total loss of mobility.

There is no treatment for this condition and, due to their poor quality of life, affected dogs are usually euthanized around two years after onset.

This disease is considered autosomal recessive, meaning that a dog must inherit two copies of the abnormal gene (one from the mother and one from the father) for his health to be affected. Dogs that inherit only one copy of the abnormal gene (from their father or their mother) will not show signs of the disease, but they will be carriers and can pass it on to their offspring.

Spinocerebellar Ataxia SCA is an irreversible progressive condition that causes degeneration in the areas of the spinal cord that carry information to the brain, producing a category of severe neuronal disorders that cause a loss of physical coordination. It is caused by a recessive mutation in the CAPN1 gene.

This variant of the disease occurs in the Jack Russell Terrier and in the Russell group terries, as well as in the Dachshund.

Affected dogs show muscle contractions (myokymia), seizures, and other signs of neurological disease.

The disease has a juvenile onset, its symptoms begin at the age of 3 to 6 months.

The first clinical signs are coordination difficulties such as balancing the pelvic limbs when walking, difficulty jumping and climbing stairs, frequent falls due to balance problems, and difficulty standing up again. The disease progresses slowly, during the later stages of the disease, walking often becomes difficult.

The average life expectancy is less than three years. For humane reasons, owners of dogs affected by this disease often opt for euthanasia.

This disease is considered autosomal recessive, this means that a dog must inherit two copies of the abnormal gene (one from its mother and one from its father) for its health to be affected. Dogs that inherit only one copy of the abnormal gene (from their father or mother) will not show signs of the disease, but they will be carriers and can pass it on to their offspring.

The juvenile encephalopathy is a serious genetic disease, it is a brain disorder associated with the PITMR1 gene.

Clinical symptoms appear early, between 6 and 12 weeks of age. Affected puppies suffer epileptic seizures. The disease progresses rapidly causing irreversible brain damage leading to death or euthanasia.

Juvenile brain disorder also includes clinical signs of recurrent seizures, behavioral changes, and coordination problems.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Dogs that only inherit the mutated gene from one parent will be carriers, will be clinically healthy, but will transmit the mutation to their offspring.

Primary lens luxation (PLL) is a painful, blinding, hereditary eye condition due to defective development or maintenance of zonular fibers, or both. The cause of PLL is a mutation in a splice donor recognition site in the ADAMTS17 gene.

This disease can be inherited or caused by trauma or a variety of conditions that affect the ocular anatomy.

The first symptoms of the hereditary form appear at the early age of 20 months, but complete luxation of the lens occurs between 3 and 8 years of age. The dog very quickly becomes blind in the first eye and weeks or months later in both eyes.

Affected dogs have painful glaucomas and blindness; the zonular fibers that support the lens in the eye break or disintegrate, causing a dislocation of the lens.

This disease is considered autosomal recessive, this means that a dog must inherit two copies of the abnormal gene (one from its mother and one from its father) for its health to be affected. Dogs that inherit only one copy of the abnormal gene (from their father or mother) will not show signs of the disease, but they will be carriers and can pass it on to their offspring.

Canine Degenerative Myelopathy (DM) is an incurable progressive neurodegenerative disease of the spinal cord. It is caused by a recessive mutation in exon 2 of the SOD1 gene.

DM is late-onset (most dogs are at least 8 years old at the onset of the first clinical signs), slowly progressive and fatal.

The initial clinical sign is characterized by general spastic and proprioceptive ataxia of the hind limbs. As the disease progresses, the frequently observed asymmetric weakness ascends to involve the thoracic extremities, resulting in paraplegia.