What is Genetics?
Genetics is the science of genes, heredity, and the variation of organisms.[1][2] The phenomenon of inheritance has been implicitly utilized in breeding of organisms and selection for desired traits, and the scientific field of genetics seeks to understand the mechanisms of inheritance.

The genetic information of organisms is contained within the chemical structure of DNA (deoxyribonucleic acid) molecules. Individually inherited traits, corresponding to regions in the DNA sequence, are called genes. Genes encode the information necessary for synthesizing proteins -- complex molecules generally responsible for enzymatic reactions, synthesis, communication and structure within a cell. DNA sequence is transcribed into an intermediate molecule called "messenger RNA", and ribosomes translate this sequence to form a chain of amino acids to form a protein. This process is known as the central dogma of molecular biology.

Although genetics plays a large role in determining the appearance and behavior of organisms, it is the interaction of genetics with the environment that determines the ultimate outcome.

The general, non-technical introduction in a nutshell is the study of how living things receive common traits from previous generations. These traits are described by the genetic information carried by a molecule called DNA. The instructions for constructing and operating an organism are contained in the organism's DNA. Every living thing on earth has DNA in its cells.

I am not a genetisist and definitly no expert but I do read and research a great deal and this is a subject that is of great intrest to me.

If anything i write you believe is not correct please let me know.

"All genetic diseases are influenced by the environment".
Dr. Padgett

The most common genetic disease in Shepherds would have to be Hip Dysplasia. This article is great in explaining it.

What is Hip Dysplasia?
Hip Dysplasia is a condition caused by a progressive deformity of the hip joints. It develops primarily in the first twelve months of age causing the `ball and socket' joints to be excessively shallow, and hence partially dislocating. The consequent instability of the hip joints results in osteoarthritic changes.

The condition affects many breeds (especially larger types), and is of particular concern to dog breeders and specialist breed clubs. Hip Dysplasia is essentially an inherited disease i.e. genetically passed on from the parent dogs. However, environmental factors such as nutrition (imbalances and/or overfeeding), exercise and trauma affecting the immature skeleton and the muscle support, also play a significant role.

Severely affected dogs may very possibly exhibit hind leg lameness under one year of age. Onset of clinical signs in moderately affected dogs can vary according to the individual's weight and level of exercise. The early signs the dog owner might notice are an increasing tendency to sit, reluctance with jumping or mounting steps, stiffness on rising and ultimately permanent hind leg lameness.

Diagnosis of Hip Dysplasia
Your veterinarian may suspect Hip Dysplasia based on a dog's breed, age, size, growth rate and presenting clinical signs. A radiograph (X-ray) is essential to determine the depth of the hip joints (which can be measured) and any osteoarthritic changes. The dog has to be positioned on its back with its hind legs extended back and parallel. The scheme stipulates that dogs must be fully anaesthetised to ensure full muscle relaxation during the radiographic procedure. Radiographs taken for Hip Dysplasia evaluation are diagnostic aids, and as such remain the property of the veterinarian as part of his/her clinical records.

Scoring system
The standardised scoring system that the NZVA Hip Dysplasia Scheme uses for dogs over twelve months of age is the same as that used in Australia and the United Kingdom. It is based on a series of nine separate scores for each hip joint, the maximum total being 106. A low combined score is desirable, with as little difference as possible between left and right.

While the ideal score is less than five, anything up to eight is considered good. Undue significance should not be placed just on the numeric score, as the range within which the score falls indicates whether the hip joints are 'excellent', 'good', 'suspect', or 'bad'.

Arithmetic mean (or average) scores are calculated for each breed and are regularly published in `NZ Kennel Gazette' and veterinary publications. The breed mean scores for some breeds are much higher than eight, so they are not necessarily a guide-line for an acceptable score.

Treatment
Anti-inflammatory or pain relieving medication may be prescribed to reduce the clinical effects of Hip Dysplasia. In milder cases weight control and sensible exercise, avoiding stressful extremes, may be adequate. In severe cases surgery may be necessary. Corrective surgery to improve the depth of the joints is only possible in young dogs before gross osteoarthritis has occurred. Otherwise artificial hip joint replacement is a possibility. Less expensive surgery is also available to ease the pain and/or restricted movement of arthritic hip joints.

Relevance of the hip score
Having had your dog scored you are faced with two considerations, these being long term prospects for fitness and for breeding. If the score is greater than eight, or greater than four on one side, it is important to discuss the relevance of the score with your veterinarian for two reasons. Firstly, it may be unwise to use the dog for breeding and secondly, the dog may show signs of Hip Dysplasia either now or later in life.

By consistently breeding only from stock achieving low scores (with no developing lameness later in life), and with as many progeny (offspring) as possible also being examined as they mature, it is possible, in time, to reduce the incidence of Hip Dysplasia.

Why is a control scheme important?
Owners choose the breed or type of dog they prefer, and it is the ethical responsibility of breeders to ensure that pups go to new homes with some guarantee of likely soundness and good health.

Many established dog breeds carry debilitating conditions which may be inherited from one or both parents. These carriers may not show any clinical signs of these conditions.

The heritability for Hip Dysplasia is quite complex. It is only through long-term adherence to a well designed, supervised control scheme that real progress can be made. This involves removing high-risk stock from the gene pool for each breed.

 

ELBOW DYSPLASIA
Introduction
Osteochondrosis is a developmental disease of growing cartilage and bone and is often a cause of lameness in young large breed dogs. The term Elbow Dysplasia refers to various forms of osteochondrosis in the elbow joint.

Presentation
Elbow Dysplasia usually manifests in three different ways:

1/ Forelimb lameness in young dogs between 4 and 12 months of age. 2/ Middle aged to older dogs that become lame and radiographs show evidence of arthritis in the elbows.
3/ Breeding dogs that are sound but produce puppies with elbow dysplasia.

Three specific forms that have been recognized are:

1/ Osteochondrosis of the medial humeral condyle.
2/ Fragmented medial coronoid process of the ulna.
3/ Ununited anconeal process of the ulna.

Studies have shown a strong hereditary basis for these conditions although certain environmental factors such as rapid growth, over supplementation and excessive exercise may make these conditions worse.

Diagnosis
Diagnosis of Elbow Dysplasia is based on confirming the presence of elbow pain coupled with the presence of radiographic changes (arthritis on x-ray). In older dogs the joint may have restricted range of movement and be swollen. A variety of radiographic views are used to examine the elbow. Often the primary cause of the lameness cannot be detected and we rely on seeing arthritis to confirm the diagnosis. In young dogs, confirmation of the diagnosis can be difficult because the dog may have elbow pain but no radiographic changes. Depending on the situation, sometimes surgical examination of the joint or repeat radiographs are required to confirm the diagnosis.

 

Treatment
Treatment of Elbow Dysplasia is aimed at minimizing the dog’s discomfort and slowing the development of arthritis. Conservative treatment such as limiting exercise, weight reduction and anti-inflammatory medication often gives relief in the short term, but often fails to slow the development of arthritis. In dogs that are persistently lame, with or without arthritis, surgical intervention is currently the treatment of choice. The surgeon removes any abnormal bone or cartilaginous fragments from the joint. Surgical results vary with the breed, extent of arthritis and type of osteochondrosis present. Even with surgery, the joint may still develop arthritis but the severity of the arthritis and joint pain is frequently much less.

Screening for Elbow Dysplasia
Some types of Elbow Dysplasia have a hereditary basis. In certain breeds a high heritability has been established. This means that there is an increased chance of a puppy developing this condition if the parents carry the defective genes. Various schemes are in operation internationally to identify those dogs carrying these undesirable traits. Screening is based on assessing a single radiograph of each elbow joint of dogs one year of age and over. The radiographs are evaluated by a panel of veterinary radiologists for the presence of arthritis. A grade is given based on the extent of arthritis present.

Control of Elbow Dysplasia
Given that Elbow Dysplasia has been shown to have an hereditary basis, it is prudent to breed only from those dogs that have no evidence of arthritis. This does not guarantee that progeny will be free of Elbow Dysplasia, but does markedly reduce the chance. Progeny testing is the ideal way to determine the success of selective breeding.

Statistics
While the individual details are confidential, the summarised breed range of scores will be integrated into international statistical data.

Selection of a new puppy
When selecting a new puppy it is wise to inquire about Elbow and Hip Dysplasia in that family. Selecting a puppy from parents who are free of these diseases will markedly reduce the likelihood of that puppy developing problems. Certain environmental factors may influence the development of elbow dysplasia. A balanced diet fed in moderation and controlled exercise during the first year of life may help to reduce the incidence and severity of this disease.

Summary
Elbow Dysplasia is a genetic disease of large breed dogs. With the increasing popularity of larger breeds, elbow dysplasia is becoming a significant problem.. Screening, controlled breeding and progeny testing will help control this disease.

 

Interpretation of Elbow Dysplasia Grade
Grading of elbows for elbow dysplasia is divided into five grades.

Grade 0:
No evidence of elbow dysplasia. This is the optimum grade.

B (borderline):
Subtle changes are seen on the elbow radiographs which are suggestive of elbow dysplasia but are of insufficient severity to be conclusive. A Borderline grade is a good score.

Grade 1:
Obvious osteophytes indicating arthrosis of the joint. In the high risks breeds this score currently represents a better than average score. In breeds with a low risk of osteochondrosis, a Grade 1 score is less than desirable.

As too many dogs have proved to fall into this category it was decided to split the grade into 1a and 1b. 1a is the more desirable grade.

Grade 2:
More severe arthrosis is present. A grade 2 score is a poor score, and breeding with dogs with this grade is not recommended. This recommendation is especially true in low risk breeds. Breeding from grade 2 dogs can be justified only if the dog has other genetic traits that would be advantageous to the gene pool of that breed as a whole.

Grade 3:
Severe arthrosis and we recommend that in no circumstances should these dogs be used for breeding.

Dogs that are scored either 0-0, 0-B or B-B in both elbows and are between 1-2 years of age at the time of radiography are eligible for a re-check when more than two years of age. Any dog with a score of 0-0, 0-B or B-B when older than two years old is given ACCREDITATION status (i.e. accredited free of elbow dysplasia by radiographic examination).

Another exellent informative site on Hip Dysplasia.

http://www.peteducation.com/article.cfm?cls=2&cat=1569&articleid=444

 

It is recomended that you get your dogs hip and ellbow scores done when fully grown at the age of two as when they are not fully grown of course things may change.

Courtesy of the NZVA Inc & the convenor of the dysplacia scheme.