Health
GUIDELINE CHART FOR PREDICTING RESULTS CAN BE USED FOR EYES (CEA) , MDR1 AND DM
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Results expected of Breeding Strategies for Inherited Recessive Diseases |
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Parent 1 DNA Tested |
Parent 2 DNA Tested |
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Clear Normal/Normal (+/+) |
Carrier Normal/Mutant (+/-) |
Affected Mutant/Mutant (-/-) |
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Clear Normal/Normal (+/+) |
All = Clear 100% N/N (+/+)
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½ = Clear 50% N/N (+/+) ½ = Carriers 50%N/M (+/-)
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All = Carriers 100% N/M (+/-)
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Carrier Normal/Mutant (+/-) |
½ = Clear 50% N/N (+/+) ½ = Carriers 50%N/M (+/-) |
¼ = Clears 25% N/N (+/+) ½ = Carriers 50% N/M (+/-) ¼ = Affected 25% M/M (-/-) |
½ = Carriers 50%N/M (+/-) ½ = Affected 50%M/M (-/-) |
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Affected Mutant/Mutant (-/-) |
All = Carriers 100% N/M (+/-) |
½ = Carriers 50%N/M (+/-) ½ = Affected 50%M/M (-/-) |
All = Affected 100% M/M (-/-) |
I use the above chart as a guide line in my breeding program. As we now have DNA testing it is another tool that can help us in doing the best we can to improve the future.
This chart is a guideline only. It also depends on what your are trying to identify and if presentation of the mutation is heterozygous or homogenous. Perfect example being MDR1, as dogs previously considered a carrier (one mutant gene) are now recognised as At Risk/Affected, because it’s now determined to be a homogenous gene mutation.
With this chart, putting Carrier to Carrier the outcome is only a guideline also as sometimes mothernature will deal you with a big variation eg all clears, all carriers or all affecteds, sometimes just one or two clears or carriers and all affecteds. Breeding has proven this to be the case in some instances.
Ophthalmology eye tested 7 ½ week old pups that come back clear are not necessarily Genetically Clear. As I have experienced myself with some results that were supposedly Clear but when DNA tested later proved to be affecteds. On speaking to the Ophthalmologist, I was advised that ophthalmology testing can sometimes be misleading as puppies eyes are so small things can be missed. I was advised it is better to also get their eyes re checked once dogs are of breeding age.
At the moment, not all, but a number of Ophthalmology tested puppies that show Clear (Normal) are in fact Carriers as we do not have a big enough Gene pool for Genetic Clears yet here in Australia. So a Clear could be a Clear or a Carrier and in rare occasions some Affecteds slip through the system.
I personally do both, as tools, as each in my opinion is equally as important as each other and will pick up on different things. I also try to keep in touch with my Ophthalmologists I use and give them the DNA results of each pup they have examined as well.
Some people have said mistakes can be made in both and yes they can, however the DNA testing has progressed and I have found to date with breeding that this chart is very accurate as a good guideline and by using both Ophthalmology Testing and DNA Testing as tools we have a better chance for getting more Genetically clear dogs a few generations on for a better future.
If a result is not what you expect then you get a second opinion. I get my puppies done both Opthalmology and DNA tested before they leave home so the owners also know the results and the cost is absorbed in the cost of the puppy.