Phenotype: Horses with skeletal atavism typically display short legs, a low rectangular shape body, narrowing at the knees, clubfoot, and impaired movement. The angles of the legs and pattern of movement progressively worsen as the foal ages, and in most cases, the horse has to be euthanized within six months.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal/Unaffected, Del1 = Deletion 1, Del2 = Deletion 2
Breeds appropriate for testing: Miniature Horse, Shetland Pony
Explanation of Results:
- Horses with N/N genotype will not have skeletal atavism and cannot transmit a skeletal atavism variant to their offspring.
- Horses with N/Del1 or N/Del2 genotype will not have skeletal atavism, but are carriers. They may transmit a skeletal atavism variant to 50% of their offspring. Matings between two carriers result in a 25% chance of producing an affected foal.
- Horses with Del1/Del1, Del2/Del2, or Del1/Del2 will have skeletal atavism.