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HIPS/ELBOWS & DNA
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PHOTO: CH TAPUA MOONLIGHT SERENADE (L) & CH TAPUA CELTIC CHARM (R)
DISCLAIMER The information stated in this section apply only to dogs owned or bred by TAPUA KENNELS. We do not assume nor expect any individual dog owner, breeder, show person or dog trainer to agree with or accept our agendas regarding the care, training, breeding or nutrition of Labrador Retrievers nor any other breed.
INFORMATION AND VIDEOS ABOUT INHERITED DISEASES IN LABRADOR ALL THE FOLLOWING CONDITIONS CAN BE ASSESSED BY DOING A FULL DNA PROFILE OF YOUR BREEDING STOCK.
INHERITED DISEASE ARE CONDITIONS WHICH HARM THE HEALTH AND WELLBEING OF YOUR DOG. MOST RESPONSIBLE BREEDERS WILL TEST FOR AT LEAST EIC & PRA. HOWEVER DESPITE ALL EFFORTS THERE ARE A LARGE NUMBER OF CONDITIONS THAT DO NOT HAVE A DNA MARKER AND A TEST DOES NOT AS YET EXIST. DNA TESTING IS A TOOL AND ONLY ONE PART OF THE ASSESSMENT OF SUITABILITY FOR BREEDING.
EIC EXERCISE INDUCED COLLAPSE: http://www.cvm.umn.edu/vbs/faculty/Mickelson/lab/EIC/retrievereic/home.html DM - DEGENERATIVE MYALOPATHY:
CNM - CENTRONUCLEAR MYOPATHY: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0046408
CYSTINURIA: http://www.caninecystinuria.com/FAQ.html
MYOTUBULAR MYOPATHY X LINKED: http://www.ncbi.nlm.nih.gov/pubmed/20682747
PRCD - PROGRESSIVE ROD CONE DEGENERATION: http://www.thelabradorsite.com/the-fight-against-pra-blindness-in-labradors/
UNDESIRABLE DNA TRAITS 'TRAITS' CAUSE NO PHYSICAL HARM TO THE DOG HOWEVER THEY MAY CHANGE THE TYPE OR LOOK OF THE LABRADOR WHICH IS UNDESIRABLE IN ANY BREEDING PROGRAM AND CAUSES DEVIATION FROM THE BREED STANDARD. COLOUR AND LONG HAIR GENE CAN BE TESTED ALSO. IN THE LABRADOR RETRIEVER THERE IS A TREND TOWARDS 'SILVER' OR 'CHAMPAGNE' COATED LABRADORS. THERE ARE 3 COLOURS THAT ARE ACCEPTABLE IN THE BREED. TO ENSURE THAT THE COLOURS CARRIED IN A MATING ARE PREDICTABLE COLOUR TESTING IS RECOMMENDED. ALSO, THE LONG HAIR TRAIT IS UNDESIRABLE. TAPUA LABRADORS SUPPORT THE PRINCIPLE THAT LABS ONLY COME IN 3 COLOURS BLACK, YELLOW AND CHOCOLATE.
SILVER COATS IN LABRADORS: http://www.labradorclubnsw.com/silver-labradors.asp LONG COAT GENE: http://www.gatewaylabs.com/html/long-coated_labradors.html
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COAT COLOUR INHERITANCE There are ONLY 3 acknowledged coat colours in Labrador Retrievers. BLACK, YELLOW & CHOCOLATE. A few breeders in the USA have managed to dilute the black & chocolate gene in their gene pool to create 'blue' or 'champagne' Labs. While novel for the pet market these dogs are generally substandard in conformation and are not bred for type, temperament and ability. Dogs or bitches may be introduced into the Australian gene pool however as a committed breeder I DNA profile all my breeding stock and can guarantee that only the 3 accepted colours will ever be produced by this kennel. Dogs producing brindle or excessive white will be removed from our breeding program.
I have found the Beulahland Kennels in the USA representation of coat colour very helpful in determining what possible combinations will occur from any given mating.
http://beulahland.tripod.com/coatcolor.htm
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GENETIC MODES OF INHERITANCE
Genetics and genetic testing are buzz concepts in dog breeding today. Terms get thrown around that are often confusing and easily misinterpreted. The following is an effort to clarify some of the genetic concepts. The challenge for a responsible breeder is to determine whether or not there are genetic issues in their lines. Many breeders struggle to determine whether a defect or disease is hereditary. Because MANY disorders in dogs do not, as yet, have a causal genetic marker identified, breeders are the first to recognise the occurrence of defects or disease in their lines from what they create in their own kennels. Honesty, diligence, and accurate record-keeping is vital. It is easy to blame the inherited abnormal genes of the dog or bitch you have used or bred from as the previous breeders 'fault' - it is what you do with the progeny of what you have chosen to create in the litter which matters.
This is a three-step method that should alert breeders that a genetic condition may exist in their lines.
1: The condition occurs more often among dogs that are related. 2: The condition increases in frequency with inbreeding. 3: The disease occurs usually at the same age for most affected animals.
There are three modes of inheritance for genetic disease and disorder:- single genes, multiple genes & chromosomal anomalies
Single Genes This is where one gene acts on its own to affect an offspring, the disease or defect is said to be caused by a single abnormal gene. There are three methods by which a single gene can cause disease or a defect. Recessive inheritance, dominant inheritance or X-linked method. (C.L.Battaglia PHD. 1995)
Recessive Inheritance Both parents carry disease or disorder on 1 abnormal gene. Although the parents themselves do not express this condition. For a pup to become affected by the recessive gene the pup must inherit both abnormal genes from each of the contributing carrier parents. If the pup inherits only one abnormal gene from a carrier parent then the condition perpetuates within the lines unexpressed until it is bred with another carrier and the abnormal condition is expressed in the progeny. The primary benefit of genetic testing is to identify carrier sires and dams prior to mating. Therefore the breeder can make an informed decision about the mating. Carriers do not necessarily need to be excluded from a breeding program however the progeny will need to be tested and clear progeny identified if the breeder chooses to eliminate the condition from their lines.
TABLE OF PROBABILITY FOR SINGLE CELL RECESSIVE GENES
Dominant Inheritance In this case, only one parent needs to have an abnormal gene in order to affect the pups and to transmit the disease of defect from one generation to the next. The severity of the condition will vary from extreme to mild. There is a myth perpetuated by some breeders that there is a 'killer gene' which will kill the affected pup in utero or at birth and therefore the other pups will not be affected. This is obviously false or else dominant inheritance would not occur. Expression of the condition at birth can be very mild and not cause any problems until later in life. Such as congenital lymphedema in GSD's.
FEMALE X - linked Inheritance The defective genes are located on the X chromosome. In dogs, as in all mammals, the female of the species has two X chromosomes and the male has an XY. All male pups receive the Y chromosome from the sire and the X from the dam. Because the Y chromosome determines the maleness of a dog the sire determines the sex of the offspring and the maleness characteristics. The X chromosome contains a large number of genes that determine the number of functions. Regarding X- linked recessive diseases the affected pups are nearly always male, who have received the affected gene from their mother. As is seen in the blood-clotting disease Hemophilia - causing death if left untreated with clotting factors.
Multiple Genes This is when more than one pair of genes interact to cause a disease or defect. The genetic cause is called polygenetic. A classic and problematic example of this is Hip Dysplasia. It has been noted since the 1950's that progeny from normal parents could be dysplastic and it has been noted that parents with dysplasia, when mated to non-dyplastic parent, produced a high number of dysplastic progeny. Whilst this suggested a dominant gene it was discovered in Sweden on GSD's that dysplasia is not caused by single-cell recessive or dominant gene methods as discussed. HD is a condition caused by the cumulative effects of a number of genes (polygenetic) which affect the development of the hip joint. Polygenetic diseases are susceptible to modification by the environment. Puppies of larger breeds should not be allowed to become excessively heavy since this directly affects the development of HD. The occurrence of HD is greatest amongst dogs who show rapid growth and weight gain in their puppy/youth age. The incident increases further in puppies that are overweight in their first 8 weeks of life.
Chromosomal Anomalies These conditions affect the XY chromosome of the male dogs. Normal dogs have 78 chromosomes, they randomly inherit 39 pairs of chromosomes from their parents and the parent's ancestors which include XY for the males and XX for females. In rare cases, the normal male inherits an extra X chromosome and become XXY. When this occurs the affected male will have abnormally small testes and will be sterile. Chromosomal abnormalities are also said to account for utero deaths and malformed pups.
For further reading on the impact of genetic disease I recommend 'Breeding For Better Dogs' Carmelo L. Battaglia PHD 5th Edition 1995. ____________________________________________________
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