Mating your dog is a process that involves research, planning, responsibility and knowledge of genetics in order to produce healthy puppies. Irresponsible breeding can lead to increased incidences of genetic disease and unhealthy puppies in both pure and mixed breeds.
How Genes Work
Dogs have 39 pairs of chromosomes that carry particular traits like coat color, size, proportion and behavior, and have two alleles for each trait. If the two alleles are the same the corresponding trait is constructed. If the alleles are different, one allele may be ‘dominant', which means if that if it is one of the two alleles, its corresponding trait will result. Each parent contributes one allele for each chromosome for a total of 39 alleles from each parent to pass on certain genetic codes. These codes allow for differences among individual dogs within a breed or species.
Abnormal or mutant alleles that can cause genetic disorders do not always express themselves. If only one parent has a dominant abnormal allele, the disease will be passed on to future generations following a dominant pattern of inheritance. Some dominant diseases are only mildly symptomatic in offspring and go undetected until a future generation shows greater symptoms. Other diseases follow a recessive pattern of inheritance and are only displayed if both parents have two of the recessives alleles, resulting in offspring with two of the recessive alleles. These recessive alleles are more likely to be exhibited in purebreds that mate with closely related dogs that may carry the same recessive alleles.
Genetic Disease
Purebred dogs are said to exhibit greater genetic diseases than mixed dogs but mixed breeds can suffer from the same genetic problems. For purebreds, inbreeding or line-breeding involves mating two closely related dogs in order to continue a certain genetic trait in their offspring. Breeding of two animals that are totally unrelated is known as out-crossing. In all these cases genetic disease may be exhibited in future generations.
That said, purebreds frequently exhibit genetic problems because they are more likely to have two recessive abnormal alleles from inbreeding than mixed breeds. By breeding purebreds with abnormal alleles with other dogs that carry a dominant allele for the same chromosome it is more likely that genetic diseases can be avoided.
Examples of genetic disease:
- Progressive retinal atrophy (PRA)
- Hip dysplasia
- Sebaceous adenitis
- Glaucoma
- Epilepsy
- Fanconi Syndrome
Autoimmune diseases
Some diseases like hip dysplasia are the result of a complicated mix of genetic code and difficult to track through inheritance. Other abnormalities like autoimmune diseases may be brought on by stress. Environment can play a factor in genetics; stressful and crowded surroundings, malnutrition in and out of the womb, infectious disease and extreme neglect can prevent a puppy from reaching its full genetic potential. Certain breeds may be more prone to genetic disease, such as blindness in English Mastiffs or hip dysplasia in large breed dogs. Understanding the risks your breed faces and your dog's pedigree are important steps before considering any dog breeding.
Responsible Dog Breeding You can't predict exactly what a puppy will look or behave like based on his parent's appearance and temperament. DNA testing and analyzing a dog's pedigree are excellent and responsible ways to determine the health of your dog and his or her future generations of puppies.
There is a great deal of debate in the breeding world about the best way to inbreed particular genetic traits rather than continuing high rates of inbreeding today. A large amount of research is currently taking place, such as the Dog Genome Project, to understand the complicated world of dog genetics and to prevent genetic disease.