The Curly Hair Test Code 353
For breeds*: Bichon Frise, Border Collie, Boykin Spaniel, Chesapeake Bay Retriever, Chihuahua, Dachshund, Havanese, Kerry Blue Terrier, Kuvasz, Leonburger, Maltese, Pharaoh Hound, Portuguese Water Dog, Soft Coated Wheaten Terrier and designer breeds based on crosses with Poodle.
*the test is offered for the breeds that are known to carry the mutation in KRT71 gene associated with the curly hair phenotype. Upon request from the owner, OptiGen will perform the test for any breed not listed above.
Hair shape, or curl, is an essential characteristic of a dog's coat and one of the most important traits in breed standards. Between the two extreme types of hair, straight and tightly curled, there is an array of intermediate types: loose curls, spiral shaped curls, waves, etc. Hair curls are most prominent on a long hair background, but their specific characteristics depend also on hair thickness, density, and the coat growth pattern. For instance, an insertion in the RSPO2 gene that is responsible for wiry hair and furnishings, produces wavy coats when it is expressed on a long hair background. When the RSPO2 mutation and the mutation associated with the curly hair trait segregate in a breed, as they do in the Portuguese Water Dog, a variety of coat types can be expected in the progeny: tight curls with furnishings, wavy coats without furnishings and flat coats with no obvious curls or waves.
Many dog breeds have been fixed for a certain coat type while some breeds still possess genetic variation for this trait and produce non-uniform progeny. Deviations from a standard coat type are not desirable and can be penalized at dog shows or be a disappointment for an owner, when a dog develops a coat type that is different from the expected and desired appearance.
A mutation for Curly Hair:
A genetic study of coat type in purebred dogs has identified a mutation in the keratin gene, KRT71, associated with the curly hair phenotype in some breeds (1). The mode of inheritance has not been determined precisely but the fact that dogs heterozygous for the KRT71 mutation do not have curls and also the occasional occurrence of dogs with curly hair in breeds with typically straight hair suggests that the curly hair is inherited in a recessive or incompletely dominant mode. The difficulty in predicting effects of the mutation in the KRT71 gene is partly explained by the variance in appearance due to the effects of other hair trait genes, e.g. hair length and furnishings.
The Curly Hair test:
The Curly Hair test allows one to determine the genotype of a tested dog as being
normal/clear of the KRT71 mutation (i.e. having two copies of the normal gene);
a carrier of one copy of the mutation; or
a homozygote for the KRT71 mutation (i.e. having two copies of the mutant variant).
Normal/Clear dogs with two copies of the wild type KRT71 gene have a predisposition to develop straight hair but they may have wavy/curly coats due to the effects of other genes. All progeny receives the normal copy of the KRT71 gene.
Carriers of one copy of the KRT71 mutation will most likely have no tight curls due to the mutation but they may have wavy coats due to incomplete dominance of the mutation or due to effects of other genes. The mutation is transmitted to about 50% of the progeny.
Homozygotes for the KRT71 mutation have a high probability of developing curly hair, especially on the long hair background. A copy of the KRT71 mutation is transmitted to all offspring.
It is recommended to test dogs for the presence of the KRT71 mutation prior to breeding to avoid producing progeny with an undesired coat type. For several breeds, including Dachshund, Portuguese Water Dog, Soft Coated Wheaten Terrier, and designer breeds based on crosses with the Poodle, that are known to segregate mutations for the KRT71 (curly hair) and the RSPO2 (wire hair and furnishings--a.k.a. "improper coat"), it is advisable to use the Curly hair and the Improper Coat test together in order to have a better predictive power when planning breeding schemes. OptiGen's DNA test for Improper Coat detects the RSPO2 insertion/furnishings trait in a variety of breeds. Both tests are available at OptiGen and receive "Combo Discount" pricing when ordered at the same time.
1. Cadieu E, Neff MW, Quignon P, Walsh K, Chase K, Parker HG, VonHoldt BM, Rhue A, Boyko A, Byers A, Wong A, Mosher DS, Elkahloun AG, Spady TC, Andre C, Lark KG, Cargill M, Bustamante CD, Wayne RK, Ostrander EA. Coat variation in the domestic dog is governed by variants in three genes. Science. 2009 Oct; 326(5949);150-153.