GENETIC TESTING FOR COAT COLOR AND LENGTH IN THE SHIBA INU
BY JACEY HOLDEN
E ver since the first draft of the canine genome was released in 2004 using a Boxer named Sasha, a few tests for different traits, both desirable and unwanted, as well as tests for various hereditary dis- eases have become available to the public through several laborato- ries specializing in animal genetics. Everyone realizes that genetics is an extremely complex science and that the majority of characteristics and conditions breeders attempt to manage in their dogs are produced by multiple genes and modifying factors that are extremely difficult to identify genetically. This, compounded by the diversity in structure and outward appearance of the many dog breeds plus conditions that are specific to one or a certain group of breeds, further complicates geneti- cists’ ability to isolate the genes that produce a certain characteristic. “46% of genetic diseases reported in dogs are believed to occur predominantly or exclusively in one or a few breeds.” (Patterson, D.F. 2000 Canine genetic disease information system: A computerized knowledge base of genetic diseases in the dog. Mosby-Harcourt, St. Louis, Missouri.) “However, the variation between dog breeds is much greater than the varia- tion between human populations (27.5% versus 5.4%). Conversely, the degree of genetic homogeneity is much greater within individual dog breeds than within distinct human populations (94.6% versus 72.5%). Furthermore, in some breeds, genetic variation has been additionally reduced by bottlenecks associated with catastrophic events such as war and economic depression.” (Ostrander, Elaine A. and Robert K. Wayne. 2005. The canine genome. Canine Genome. Cold Springs Harbor Laboratory Press) In other words, what is geneti- cally accurate in one breed, or many breeds, may not be true in all breeds but, because of controlled breeding, individuals within a breed are much more genetically uniform than humans from a specific region. Thus, each breed must be studied individually. Once specific genes known to cause a certain characteristic or condition have been isolated, it is another step to offer testing for those genes to the general public. Genes affecting coat color and length are some of the easiest to quantify. It appears that most breeds have the recessive gene for long-coats. A long-coated Rottweiler may not be a fluffy dog like a long-coated Shiba, but the identified gene is the same in both (it appears that another gene may be involved in long-coated Siberians and Akitas, but it was not seen in Shibas) and several animal genetics laboratories offer tests for this gene. If a dog does not carry the long-coat gene, it is labeled LL where L is the dominant form of the gene. If it is a carrier but does not exhibit the long-coat, the dog is Ll where l is the recessive gene version. If the dog has a long-coat, the genes are ll . If an LL is bred to another LL , no long-coats and no carriers, Ll , will be produced. If LL is bred to Ll , no long-coats will be produced, but half, on average, will be Ll long-coat carriers. If Ll is bred to Ll (again extrapolated out over the popu- lation), out of four puppies, one puppy will be LL and not a carrier, two will be Ll carriers, and one will be an ll long-coat. The ratio of genes L or l that goes
Long-Coat Cream (photo courtesy of Lori Pendergast)
Cream puppies never have a black hair from birth. (photo courtesy of Susanne Ozasa)
232 | SHOWSIGHT MAGAZINE, MAY 2022
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