When were Ridgeback's first bred?
Rhodesian Ridgeback
The only disqualification in the AKC standard for this breed is "ridgelessness". This term refers to the purebred offspring of heterozygous parental animals that do not inherit a copy of the ridge mutation from either parent and are, in effect, normal dogs without a ridged back. The most current research suggests that the ridge mutation is autosomal dominant with complete penetrance. However, while the few studies that have analyzed the issue do not agree on the incidence of ridgelessness within the breed, they all show a ridgeless rate significantly lower than 25%, which cannot be explained using the Punnett square model for single gene/two allele inheritance.