Miroslav Hornak, Ph.D.
Genetics and Reproduction
Veterinary Research Institute
Hudcova 70
621 00 Brno
Czech Republic
tel.:     +420 776 850 577

Test for ridge disposition in Rhodesian ridgeback

The Rhodesian ridgeback's distinguishing feature is the ridge of hair running along its back in the opposite direction from the rest of its coat. This characteristic is genetically determined and governed by the dominant inheritance. To understand dominant inheritance, it is necessary first to realize that every dog ​​has inherited from its parents, two copies of each gene (one from its mother and one from its father).

Dominant inheritance means that if the puppy inherited the ridge gen just from one parent, there ridge is formed on the puppy´s back. In this case, the dog with only one ridge gene is called heterozygote (Rr). If the dog inherited ridge gene from both parents, the dog has two ridge genes, will form a ridge on the back and is called dominant homozygote (RR).

However, in the litter there may ridgeless puppies. Ridgeless puppies are born to two heterozygotes (male and female dog with only one ridge gene). Statistically, in a litter of two heterozygotes there will be born 25% ridgeless puppies .

However, according to the test results in practice, it appears that the ridge genetics in Rhodesian ridgebacks is not so simple and is characterized by incomplete manifestation of ridge gene. This means that all dominant homozygotes have ridge. Also, approximately 90% of the heterozygotes have ridge, but 10% of the heterozygotes are ridgeless. Very likely, the ridge gene is suppressed and ridge is not formed on the back. All individuals who lack ridge gene (rr) are ridgeless.

In collaboration with the Veterinary Research Institute in 2014, we have for the first time developed the genetic test, which distinguishes dominant homozygotes (two ridge genes) from heterozygotes (one ridge gene). This is the most accurate way how to predict birth of ridgeless puppies, if both parents are tested (see. Table below). Our test determines whether and to what extent there will ridgeless puppies in a litter!

Further, it was also observed the association between genetic disposition for the ridge and the occurrence of dermoid sinus. According to the research, dermoid sinus occurs approximately 5 times more often in dominant homozygotes. Our test may reduce the incidence of dermoids in Rhodesian Ridgebacks by a controlled selection of tested individuals for mating.
The test can be performed from 0,5-1ml collected blood or buccal swab.
For further questions, please contact us. If you are interested in our genetic test, you will find all the information in the section order test.