Phenotypic test vs genetic
testing what’s the difference?
In our
breed we have a set of heritable diseases and two traits that we can
test for
Hips,
Elbows,
Eyes,
Heart,
Jlpp (fatal in pups under a year old)
,Lemp (appears after a year old),
Nad (appears after a year old)
,XLMTN (fatal in puppies, not common in USA),
DM (test shows susceptibility only),
Long coat, Furnishings.
Genetic (DNA)
tests come in two forms
Marker test
and Linkage tests.
Marker tests are always far more
accurate and reliable than linkage tests. (FYI Embark uses many linkage
tests ).
Genetic tests must be
validated on each breed it’s used on before relying on it for breeding
decisions.
We have validated Genetic marker tests
available for the following recessive diseases which are totally
accurate:
*Jlpp, *Lemp, *NAD,
*XLMTN
And
For the following two traits
which are totally accurate:
*Long coat (accurate ONLY if tested at a laboratory that tests for all
5 variants -UC Davis is one such lab)
*Furnishings
We also have a genetic marker test for
DM susceptibility . DM is a recessive disease that has incomplete
penetrance which means dogs with the genes for this disease may or may
not ever develop it.
Dogs with two copies of the DM gene have a risk of developing this
condition at some point in their life but it’s not guaranteed.
Phenotypic tests
Phenotypic tests are tests that diagnose
dogs based upon what can be seen, but do not tell you what genes the
dog carries.
To determine what genes a dog carries
for these disease requires researching as many relatives as you can
find- not just parents, grandparents etc, but also siblings, half
siblings, aunts, uncles, cousins and even then you don’t know for sure
with 100% positivity.
For this reason, dogs that are
phenotypically clear of the diseases may still produce the disease in
their offspring. The best defense against this - to the best of our
ability- is researching the family and choosing animals from families
with low incidence.
Heritable
Diseases for which we have phenotypic tests for are:
* hip dysplasia
*elbow dysplasia (ED is comprised of three different diseases Uap, FCP
And OCD)
*eye diseases (several different disease in the breed)
*SAS cardiac disease (along with occasional MVD and rare
cardiomyopathies)
For these
diseases you use dogs clear of the diseases by phenotypic tests,
understanding that they are not a guarantee the dogs will not produce
the disease. But, they do assure you that you are not using an affected
dog in your breeding program. (Use of affected dogs dramatically
increases odds of producing seriously affected offspring)
You can increase your odds of avoiding
serious versions of these disease by doing the family research
mentioned above. For example a dog with of a excellent hips but a
family of mostly fairs or fails is a bad breeding prospect. While a dog
with fair or good hips whose family are mostly good or excellent with
no fails is a great prospect. A family that produces multiple moderate
or severe hip dysplasia is a bad breeding risk.
Phenotypic Cardiac exams have long been
controversial for this reason, with many feeling the extra cost to have
a cardiologist echo performed is not worthwhile since two clears can
still produce SAS.
However, we know that dogs that pass
cardiologist auscultation only exams are often found to be actually SAS
affected when echocardiogram is done.
You would not breed a dog with failing
hips, don’t risk breeding a dog with heart disease
Health testing is just
one part of choosing breeding dogs, but it is the foundation upon which
you build the rest of the dog on
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