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Canine Genetics
(Results From One Of Our 2nd Generation Show Line
German Shepherd Females From A Wisdom DNA Test Panel)
Learn More...
Note: French's German Shepherds should probably have asked the doctors owning our dogs to write this page...
The discoverer of modern genetics was Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied "trait inheritance," patterns in the way traits are handed down from parents to offspring. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance."
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.
Dogs are known to have a total of 78 chromosomes, and can be classified into 38 pairs with two sex chromosomes. In both humans and dogs, females have two copies of the X chromosome, while males have one X and one Y chromosome. The canine genetic “library” has now doubled to 5 billion bases, across 78 chromosomes. Elimination of inherited genetics defects should be of the highest importance to breeders. Dogs outnumber all other species in the number of documented genetic disorders and many are specific to specific purebred breeds. Available genetic tests for these thousands of inherited disorders are very small in number by comparison, but are rapidly developing. Read What does "Health Tested" Really Mean...
Below is an explanation of the gene
contribution percentages in each generation that
progeny
offspring receive. The top row of small
unlabeled boxes indicate Great, Great,
Grandparents at 6.25%. Not every
offspring in a litter will receive the same
identical genes. In
canines, identical twins are almost
non-existent. Not shown is that Great,
Great, Great, Grandparents contribute
3.125% of a dog's gene totals.
It is a genetic fact that every living thing is the inherited sum of all its collective ancestors - for better or for worse.
It has been estimated that genetics account for approximately 35% of performance. The remaining 65% is attributable to other influences such as environment, overall care, training, management and nutrition. Included in these dynamics is the role of the whelping mother, her health and nutrition, and the feeding and nurturing of her puppies. So not only prenatal, but postnatal effects can contribute to influences in offspring. When breeders conduct Early Neurological Stimulation, proper socialization, good nutrition, and immunizations, there is a good basis for understanding how much breeders actually contribute to your dog. Read More... and More Here...
Below is graph showing the genome wide diversity from a genetic testing panel from one of our 2nd generation Show Line females, Karma Carmella:
Autosomal Recessive Genes Pass Rate To Progeny
Conscientious reputable ethical breeders are involved in continuing genetic education. They will take advantage of advancements in science and medicine especially as it relates to DNA testing and genetic disease prevention. For our commonly used breeding animals, we use the Wisdom Panel and Embark to screen for multiple Genetic Health Conditions. View actual Embark Test Results for our breeding female Octavia "Ava" and from our Wisdom Panel DDR breeding female "Venus." Often when we use DNA genetic screening for specific tests, we also use GenSol Diagnostic and DDC Veterinary.
We do not want the lineages and progeny of the dogs we have bred to contribute or add to health problems prevalent in the breed of the German Shepherd dog realizing that other purebred breeds of dogs also have unique genetic health problems . This is why our breeding animals are registered by the Orthopedic Foundations for Animals (OFA) by X-ray for Hip and Elbow Dysplasia, Degenerative Myelopathy and Temperament, and we make the results available online to the general public. Genetic Health is an important factor in our breeding program and we utilize selective breeding practices to improve our breed. Read Approaches to Combating Inherited Disease...
Genetic disease is common in all dogs, especially purebred dogs. A huge problem in purebred dogs is the issue of the "Popular Used Sire Syndrome" also known as "Frequently Used Sire (FUS)." Popular sires, or male dogs that are used to produce large numbers of puppies are one of the biggest contributors to a reduction in genetic diversity, an increase in inbreeding and elevated levels of genetic diseases within a breed. These dogs are often chosen because they are top winning dogs, have good characteristics, such as traits associated with good health and winning awards in performance and competition. Breeders will mate these dogs because they wish to improve the breed, but over-excessive use of any one breeding male whose progeny are also used for breeding can create a significant impact to an over-all purebred population. Read About German Shepherd Color Inheritance...
Such male sires that are over-excessively are called "Matadors." Matadors are male dogs that produce hundreds, if not thousands of offspring spreading their genes through their bred progeny (including defective genes) thereby making a significant impact on their breed. Over-excessive use of "Matadors" can spread recessive genetic defects in a breed that may take generations of selective breeding to eliminate. The German SV states that a stud dog may at the most do 60 breedings to bitches from his homeland and up to 30 breedings for foreign females and Artificial Insemination (AI) is not allowed. Dogs are then often sold and exported to another country as the United States where there are no limitations on breedings. Note: Excellent prepotent sires producing great progeny dogs can and should be utilized excessively, as long as only a limited number of progeny are allowed to be bred.
The American Kennel Club’s is the first all breed registry to require DNA profiles for stud dogs routinely siring litters. Effective for litters whelped on or after July 1, 2000, every sire producing seven or more litters in a lifetime or producing more than three litters in a calendar year must be "AKC DNA Profiled." These DNA profiles will be used for genetic identity and for parentage verification, and, thus, will be used to advance issues relating to the integrity of the registry. Yet these DNA profiles are for determining parentage for the integrity of the Registry, not for determining genetic defects or inherited health issues.
There are 4 Modes of Genetic Inheritance:
Autosomal Recessive gene located on any chromosome except sex chromosome - requires both parents before the genetic effect appears in offspring
Autosomal Dominant gene located on any chromosome - requires only 1 parent before the genetic effect appears in offspring
Sex Linked gene either recessive or dominant and located on either the x or y sex chromosome before the genetic effect appears in offspring
Polygenic Inheritance is when one of more genes from each parent (each parent does not have to contribute equal genes) - requires a threshold sum or additive effect of exceeding certain amounts before the genetic effect appears in offspring
Any discussion of Chromosomes and Genetics usually includes the subject of "Mutations." Whenever a cell divides, it makes a copy of its DNA and sometimes that copy is not exact. Any difference in the copy may be called a mutation. Random mutations are by definition, "abnormalities or mistakes" most of which are harmful.
Even in the most isolated and pristine environments, mutations occur by a breakdown of DNA. They are not all naturally occurring as mutations can also be caused by environmental exposure to chemicals and radiation. Cells have an ability to repair DNA, but not necessarily perfectly. For example here are Point Mutations, Deletion Mutations, Duplication/Insertion Mutations, Inversion Mutations, and Frameshift Mutations.
Reputable and Ethical Breeders guarantee their dogs, and are always be willing to refund or take back and replace a dog with proven serious genetic health or temperament issues. Even when ethical breeders health test parents and study each dog's pedigree in advance of a breeding, there is no guarantee that a dog will not inherit a genetic condition that existed many generations ago in their lineage and unexpectedly reoccurs regardless of the best efforts of breeders.
There are multitudes of possible genetic combinations, epistatic genes, mutations, recessive genes, polygenetic inheritance, heterozygous genes, mitochondrial thresholds, pleiotropic, and other heritable dynamics that can appear in offspring. Science has discovered the field of "Epigenetics," the term used to describe inheritance by mechanisms other than through the DNA sequence of genes working through chemical tags added to chromosomes that in effect switch genes on or off.
The most serious genetic health problems are often referred to as the "Dreaded Disorders." These genetic health disorders include diseases and health issues that cause an animal to live in pain, cripple, kill, cause early death or result in blindness.
The Power of Epigenetics
Most dog breeders know the importance of genetics but epigenetics is equally important. Epigenetics captures the influence of the environment on how our dogs’ genes are expressed. These influences range from our dogs’ nutrition and the care we give them, to their internal environment, like stress. Not only do these influences affect our dogs but some will be passed on to their progeny.
Control of Canine Genetic
Diseases by George A. Padgett, DVM
A Howell Dog Book of Distinction, this
provides an expert road map to help dog
breeders everywhere avoid the pitfalls
they are almost destined to encounter.
For anyone whose goal is to produce
healthy, functional and beautiful dogs,
this is the book they need. Dr. Padgett
provides clear explanations of modes of
inheritance, how to conduct and analyze
test matings and how to lower the chances
of producing affected animals. Numerous
tables, diagrams and graphs further
enhance the text to facilitate the
breeder's understanding.
The Genetic Connection: A Guide
to Health Problems in Purebred Dogs by
Lowell Ackerman, DVM, PhD, Dipl. ACVD
The most complete collection
ever assembled of breed-specific
information for the diagnosis and
treatment of medical conditions with a
genetic basis. For the veterinary
practitioner and the serious breeder, The
Genetic Connection covers more than 240
genetic disorders, including how they are
genetically transmitted in different
breeds, how they are best identified, and
strategies to help prevent them from
occurring in future generations.