Ridge
Ridge
General description
The characteristic dorsal ridge of the Rhodesian Ridgeback arises from a genetic variant on chromosome 18 and appears as a strip of coat in which the hair grows in the opposite direction to the rest of the coat. A genetic test can determine whether the ridge gene is present in the heterozygous (R/r) or homozygous (R/R) form. Based on the genotypes of the breeding partners, it is possible to predict whether the offspring may include puppies without a ridge.
Breeds
Rhodesian Ridgeback
Order details
| Test number | 8970 |
| Sample material | 0.5 ml EDTA blood, 2x cheek swab, 1x special swab (eNAT) |
| Test duration | 7-14 working days |
Test specifications
| Inheritance | autosomal dominant with incomplete penetrance |
Detailed description
A characteristic feature of the breed Rhodesian Ridgeback is the ridge: a clearly defined strip along the back in which the hair grows in the opposite direction to the rest of the coat, meaning it is oriented from back to front.
The appearance of the ridge is clearly defined by the respective breed standards. In the Rhodesian Ridgeback, the ridge should begin directly behind the shoulders and run centrally along the back up to approximately the level of the hip bones, becoming slightly narrower towards the rear. It should be clearly distinguishable from the surrounding coat and ideally have a width of around 4–5 cm in the shoulder area. Within the ridge, two hair whorls (so-called crowns) may form, which should ideally be positioned opposite each other in a mirror-image arrangement.
The expression of the ridge is caused by a genetic variant in the Ridge gene on chromosome 18. This variant is a duplication of a 133 kb DNA segment that includes several genes from the FGF family (FGF3, FGF4, FGF19, ORAOV1) as well as surrounding regions. It is an autosomal dominant variant with incomplete penetrance. The following genotypes may occur:
- r/r: without a ridge (ridgeless); the ridge variant is not present and cannot be passed on to offspring
- R/r: heterozygous; one copy of the ridge variant is present and can be passed on to offspring with a 50% probability; 95% of R/r dogs have a ridge, while in approx. 5% of R/r dogs the dominant R allele is silenced, meaning these dogs do not develop a ridge
- R/R: homozygous; two copies of the ridge variant are present, and the variant is passed on to 100% of the offspring
Using the genetic test, it is possible to determine whether the ridge gene is present in the heterozygous (R/r) or homozygous (R/R) form. Thus, based on the genotypes of the mating partners, it can be predicted whether puppies without a ridge may be expected in the litter.
There is evidence that discrepancies from the desired appearance of the ridge, such as a shortened or partial ridge or the presence of more than two hair whorls (crowns), may occur more frequently in dogs with the R/R genotype. However, the exact correlations have not yet been fully investigated.
