Genetics and the Dog: Breed Action

In some breeds, admitting to the occurrence of an inherited defect is hazardous. Many breeders will openly condemn those who confess to having had a problem. It is as if breeders believe that silence will make the defect go away. This is clearly not the case, indeed, it is more likely that defects will spread. It is far more mature to admit to problems and collectively try to solve them. In the short term there may be heartache and economic loss for some, but in the long term the breed will benefit. It is crucial that breeders do not simply rely on pedigree data vvhen trying to evaluate problems. If a defect is recessive or suspected as being recessive, then the need is not only for five generation pedigrees of affected animals but also numbers of the litter born, their sexes status and, in the case of defects seen in later life, the age at examination. Given such data, a geneticist can help a breed examine the problem in depth. Given a list of “affected” pedigrees only on is in danger of “tracing the defect to a certain dog” without being aware that all pedigrees, affected and normal, trace to him. Any widely used stud might appear in “affected” pedigree without actually being the source of the problem though in some cases may prove to be.

Table 3 Some canine defects known to be of simple inheritance
Defect Mode of inheritance Principal Breeds Affected
Skeletal and General
Chondrodysplasia Autosomal Recessive Alaskan Malamute
Carpal subluxation Sex linked Recessive Irish Setter cross (exp)
Dew claws (rear) Dominant Most breeds
Ehlers-Danlos Dominant ESS
Pituitary dwarfism. Autosomal Recessive GSD, Karelian Bear Dog
Long coats Autosomal Recessive Seen in many short-coated breeds, eg, GSD, Basset. Some breeds are long-coated and thus carry the recessive gene twice.
Afibrinogenaemia Autosomal Dominant St. Bernard
Cyclic Neurtropenia Autosomal Recessive Collie (Rough)
Factor VII deficiency Autosomal Recessive Beage, Alaskan Malamute
Factor X deficiency Incomplete Dominant Spaniel (Cocker)
Factor XI deficiency Incomplete Dominant ESS
Haemophilia A Sex linked Recessive Most breeds
Haemophilia B Sex linked Recessive Cairn Terrier, French Bulldog
Von Willebrand’s Dominant (lethal) GSD, Golden Retriever, Scottish Terrier, Dobermann, Miniature Schnauzer, Chesapeake Bay Retriever.
Cardiovascular Lymph System
Lymphodaema Dominant Labroador/Poodle cross (exp)
Cataract (juvenile) Autosomal Recessive GSD
Cataract Autosomal Recessive Boston Terrier, Afghan, OES, Miniature Schnauzer, Poodle (Standard)
Collie Eye Anomaly Autosomal Recessive Collie (all types)
Hemeralopia Autosomal Recessive Alaskan Malmute
Lens luxation Autosomal Recessive Tibetan Terrier (may be same mode in other breeds)
PRA (general) Autosomal Recessive Irish Setter, Poodle, Tibetan Terrier, Spaniel (Cocker), Elkhound, Welsh Corgi (Cardigan)
PRA (centralized) Autosomal Recessive (most likely cause) Briard (may apply to other breeds)
Retinal dysplasia Autosomal Recessive ESS, Retriever (Labroador), Bedlington Terrier
Ceroidlipofuscinosisq Autosomal Recessive English Setter
Congenital myasthenia gravis Autosomal Recessive Fox Terrier (Smooth)
Diseases of cerebellum (PNA, Ataxia etc)* Autosomal Recessive Kerry Blue Terrier, Collie (Rough ), Fox Terrier
Familial amaurotic idiocy Autosomal Recessive German Short-haired Pointer
Globoid leukodystrophy Autosomal Recessive Cairn Terrier, WHWT
Progressive axonopathy Autosomal Recessive Boxer
Scottie cramp Autosomal Recessive Scottish Terrier

(exp) = located in experimental breeding unit of dogs
* These diseases vary in format but are all known to be recessive.
This list is not comprehensive in defects or in breeds. Defects of more complex inheritance are excluded.