What is Autosomal Dominant Inheritance?
The risk that your animal may exhibit or pass on a trait or disease to its offspring depends on the mode of inheritance.
The term autosomal refers to a non-sex chromosome (neither X nor Y). Meanwhile, dominant means that a single copy of the mutation—whether inherited from the mother or the father—is enough for the disease or trait to be expressed.
In dogs, as in humans, alleles are inherited in pairs—one from each parent.
In the case of an autosomal dominant disease, only one of the two genes needs to carry the mutation for the dog to develop the disease (N/M, Carrier).
How is such a disease transmitted?
A parent affected with two copies of the mutated gene:
If a dog is affected by an autosomal dominant disease and carries two copies of the mutated gene (homozygous for the mutation), it will always pass on the mutated gene to its puppies. Each puppy will therefore inherit one copy of the mutated gene and will be at risk of developing the disease.
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A parent carrying one mutated copy and a healthy parent:
If a dog carrying a single copy of the mutated gene (heterozygous for the mutation) is bred with a healthy dog (who does not carry the mutation), each puppy has a 50% chance of inheriting the mutated gene—and therefore potentially developing the disease—and a 50% chance of inheriting the normal gene and being healthy.
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Two parents carrying one mutated copy:
If both parents carry the mutated gene, each puppy has:
- a 25% chance of inheriting two normal copies of the gene (healthy),
- a 50% chance of inheriting one normal copy and one mutated copy (affected),
- a 25% chance of inheriting two mutated copies, which may result in a more severe form of the disease.
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Two parents carrying two mutated copies:
If both parents carry two copies of the mutated gene (MM), each puppy will inevitably inherit two copies of the mutated gene, and all puppies will be affected by the disease in a severe form.
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One parent carrying two mutated copies and one parent carrying a single mutation:
Each puppy has:
- a 50% chance of inheriting one normal copy and one mutated copy (affected),
- a 50% chance of inheriting two mutated copies (affected).
These puppies will inherit one mutated copy from the affected parent and one normal copy from the carrier parent. They will carry the mutated gene but may show variable symptoms depending on the gene’s penetrance and expressivity.
How can this disease be prevented?
Genetic testing:
Before breeding dogs, it is essential to perform genetic testing to identify carriers of mutations responsible for autosomal dominant diseases.
Breeder selection:
Avoid breeding dogs that carry two copies of the mutation. If a dog carrying a single copy is used for breeding (due to desirable physical or behavioral traits), it should only be bred with a dog that has been tested and confirmed healthy.
Controlled breeding programs:
Work with veterinarians and genetic specialists to establish breeding programs aimed at reducing the prevalence of genetic diseases in the canine population.
Conclusion:
Autosomal dominant genetic diseases can be effectively managed through genetic testing and careful selection of breeding dogs. By taking these precautions, breeders can reduce the risk of transmitting these diseases and improve the overall health of their canine lines.